Rich and Eazy Lentil French Onion Soup

Hearty, Rich & Easy

• Prep Time: 10 minutes
• Cook Time: 25 minutes
• Total Time: 35 minutes
• Cost per Serving: Under $3
• Calories per Serving: ~290 kcal

This Lentil French Onion Soup is one of those recipes I wasn’t sure would actually work the first time I made it. I mean, French onion soup is already kind of a big deal — rich, slow-cooked, golden perfection in a bowl. And lentils? Well, they’re not exactly known for making things fancy.

But then I tried it. And let me tell you: it just works.

The caramelized onions bring that deep, sweet-savory flavor you expect from the classic, while the lentils add a heartiness that turns this into a full-on, one-bowl dinner. Add some toasted bread and melty cheese on top, and suddenly this humble soup feels kind of elevated — like it should’ve always been made this way.

What I love most? It’s way easier than it looks. TheLentil French Onion Soup is mostly hands-off, and it’s meatless, nourishing, and super comforting — exactly what I’m looking for on a weeknight when everyone’s hungry and bedtime is closing in.

Why you will love Lentil French Onion Soup recipe

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Because it tastes way fancier than the effort you’ll actually put in — and honestly, that’s a rare win in mom life.

This soup hits that perfect spot between comfort food and practicality. It’s rich and cozy thanks to the slow-cooked onions, but the lentils add enough protein and texture to make it feel like a real meal — not just a side or a starter.

You don’t need beef broth. You don’t need wine. You don’t even need hours. Just a handful of pantry ingredients, one pot, and a little patience while your onions do their thing.

It’s meatless, nourishing, freezer-friendly, and the kind of meal that somehow impresses everyone at the table — even if you’re still in sweatpants.

How to make Lentil French Onion Soup recipe

You will need

You’ll find exact measurements and quantities below in the full recipe card.

Yellow Onions: The heart and soul of this recipe. Go for large yellow onions — they caramelize beautifully and bring that sweet, golden richness that defines a proper French onion soup. Slice them thin for even cooking, and give them time to do their thing.

Garlic: Just two cloves, minced fine. They sneak in at the end of the caramelization, adding a quiet depth and warmth without stealing the show.

Olive Oil: Two tablespoons might sound like a lot, but remember — we’re not just cooking here, we’re coaxing out flavor. Olive oil gives the onions that glossy, slow-cooked texture you’re after. Use the good stuff if you can.

Balsamic Vinegar: One tablespoon is all you need. It adds a little acidity to balance the sweetness of the onions, plus that deep, almost wine-like complexity.

Dried Thyme: A teaspoon brings in that comforting, herbaceous note you expect in classic French onion. You could use fresh if you have it, but dried works perfectly here.

Cooked Lentils: Brown lentils are ideal. They hold their shape, add plant-based protein, and soak up flavor like little sponges. You can use pre-cooked or canned — just rinse well.

Vegetable Broth: The base that ties it all together. Choose low-sodium if you want more control over the final seasoning. Bonus points for homemade, but boxed broth works just fine.

Soy Sauce (Optional): A tiny splash adds umami depth. Totally optional, but it really does elevate things.

Bread & Cheese: The top layer is what makes this soup feel indulgent. Use crusty bread (like baguette or sourdough), and shredded Gruyère or Swiss for that classic melted finish. Want it dairy-free? A plant-based cheese works here too.

Step-by-Step Instructions

Step 1: Slice your onions — yes, all of them
Grab four large yellow onions and slice them thin. This is the most time-consuming part of the recipe, but also the most important. Thin slices mean even caramelization.

Step 2: Start caramelizing
In a large Dutch oven or deep pot, heat 2 tablespoons of olive oil over medium heat. Add all the onions and a pinch of salt. Stir to coat, then cook for about 20 minutes, stirring occasionally. You want them golden, soft, and jammy.

Step 3: Add flavor boosters
Once the onions are caramelized, stir in the garlic and cook for another minute. Add the balsamic vinegar and thyme, and stir well to deglaze the pot. Scrape up any golden bits from the bottom.

Step 4: Build the broth
Pour in the vegetable broth and stir in the lentils. Add a splash of soy sauce if using. Bring everything to a gentle simmer and cook uncovered for 10 to 12 minutes.

Step 5: Toast the topping
Slice your bread and toast it. Then top with shredded cheese and broil for 2 to 3 minutes until melted and bubbly. Watch closely — cheese burns fast.

Step 6: Serve and savor
Ladle the soup into bowls and top each one with a slice of cheesy toast. Serve hot.

Lentil French Onion Soup Recipe Tips

Don’t rush the onions
Letting them caramelize properly is where all the flavor happens. Keep the heat on medium-low, stir occasionally, and give it time. It’s worth it.

Use pre-cooked lentils
To keep it weeknight-friendly, go with canned or pre-steamed lentils. Just rinse them first. They hold their shape and absorb flavor beautifully.

Balsamic vinegar makes a difference
That splash of acid brightens the sweetness of the onions and replaces the wine you’d find in the classic version.

Top it your way
No Gruyère? Try Swiss, mozzarella, or a dairy-free option that melts well. Use any crusty bread you have on hand — as long as it holds up to the broiler.

Freeze without the bread
This soup freezes well. Let it cool completely and store in portions. Add fresh toast and cheese when you reheat.

Perfect pairing

This soup is plenty satisfying on its own, but if you want to round out the meal, here are a few simple ideas.

A crisp green salad with lemon vinaigrette adds freshness and brightness. Arugula, spinach, or mixed greens all work well. Add thinly sliced apple or pear if you have them.

Roasted veggies — like carrots or sweet potatoes — complement the soup’s richness and add texture.

Extra cheesy toast is never a bad idea. Serve some on the side for dipping or let the kids make their own cheesy “boats.”

For dessert, keep it light. A baked apple, some dark chocolate, or even Greek yogurt with a drizzle of honey is the perfect finish.

Love lentils as much as we do? Don’t miss our Trader Joe’s Lentil Soup Hack — it’s creamy, cozy, and ready in just 20 minutes. Perfect for those nights when you want something warm without turning on the stove for an hour.
Get the recipe here

Kitchen tools youl need

1. Dutch Oven or Heavy-Bottom Soup Pot
Perfect for slow-cooking onions without burning them. It holds heat evenly and gives your soup that deep, developed flavor — all in one pot.

2. Wooden or Silicone Spoon
Gentle on your cookware and sturdy enough to stir a big batch of onions as they caramelize. A go-to in any busy kitchen.

Frequently Asked Questions about Lentil French Onion Soup

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Lentil French Onion Soup

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★★★★★

5 from 3 reviews

• Author: savorathomeHeart
• Total Time: 35 minutes
• Yield: 4 1x

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Description

A cozy one-pot soup that brings together rich caramelized onions, hearty lentils, and cheesy toasted bread. This vegetarian French onion soup is comforting, flavorful, and easy enough for a weeknight dinner.

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Ingredients

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• 2 tbsp olive oil
• 4 large yellow onions (thinly sliced)
• 2 cloves garlic (minced)
• 1 tbsp balsamic vinegar
• 1 tsp dried thyme
• salt and pepper (to taste)
• 4 cups vegetable broth (low-sodium)
• 1.5 cups cooked brown lentils (or 1 can, rinsed and drained)
• 1 tsp soy sauce (optional)
• 4 slices crusty bread (baguette or sourdough)
• 1 cup shredded Gruyère or Swiss cheese (or dairy-free alternative)

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Instructions

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Heat the olive oil in a large Dutch oven or heavy-bottomed pot over medium heat. Once hot, add the onions along with a pinch of salt. Let them cook slowly for about 20 minutes, stirring occasionally, until they turn soft and beautifully caramelized. Add the minced garlic and cook for another minute, just until fragrant. Stir in the balsamic vinegar and thyme, scraping up any browned bits from the bottom of the pot to build flavor.
Next, pour in the broth and add the cooked lentils. If you’re using soy sauce for an extra umami kick, stir it in now. Let everything simmer together, uncovered, for about 10 to 12 minutes so the flavors meld.
While the soup simmers, toast the bread slices. Once crisp, top each slice with cheese and broil them for 2 to 3 minutes until the cheese is bubbly and golden. To serve, ladle the soup into bowls and top each one with a cheesy toast. Finish with a sprinkle of black pepper or fresh thyme for a cozy, comforting touch.

Notes

French lentils work great if you want more texture.
Store leftovers in the fridge for up to 4 days.
Soup can be frozen without the bread topping.
Make it gluten-free with GF bread and dairy-free with plant-based cheese.

• Prep Time: 10 minutes
• Cook Time: 25 minutes
• Category: Soup
• Cuisine: French

Nutrition

• Calories: 290
• Sodium: 540
• Fat: 12
• Saturated Fat: 4
• Carbohydrates: 32
• Fiber: 7
• Protein: 14

Keywords: cozy dinner, french onion soup, lentil soup, meatless, one-pot meal, plant-based, vegetarian