French onion lentil and spinach soup

This soup is healthy, warming, comforting, and filled with iron and fiber. It also tastes better the second day, so double the batch and enjoy the leftovers all week!

Take me to the recipe!

I started making this soup when I was pregnant with Z and the thought of eating meat really turned my stomach. I was looking for nourishing soups that also tasted great and kept me full because while I LOOOOOOVE a soup, they don’t always fill me up unless they’re cream-based or more of a stew.

Enter this soup. It starts off with a base of caramelized onions like you’re making French onion soup. I use a super-quick method for caramelizing onions that might take a minute to get the hang of, but turns raw onions into melty, caramelized goodness in about 20-25 minutes instead of 45-60 minutes. I outline the process here.

Basically, you’re using high heat and a covered pan while also de-glazing every 2-3 minutes to achieve that deep, rich color and flavor by utilizing all of the stuck on bits at the bottom of the pan. It can be tricky to find that sweet spot between browning and burning, but luckily, the onions are pretty forgiving and if they get a little too dark, you can just deglaze with a bit of extra water and turn the heat down a smidge.

Once you have those jammy onions in the bag, you can basically add the rest of the ingredients (with a little watching for a few minutes) and let the stove do the rest of the work.

This soup makes me so so happy. I’ve made it for new moms during those rough postpartum days. I’ve also made it for snow days and arctic days, regular days and special days. I always wish I was eating it in front of a fire wearing a huge sweater and reading a book, but alas, that never happens.

French onion lentil and spinach soup

5 cups sliced onions (about 3 large onions, sliced 1/8th of an inch thick)
3 Tbsp butter or olive oil (or a combo)
2 cups water
½ tsp dried thyme or 2 sprigs fresh thyme
1 tsp kosher salt 
1 Tbsp red wine vinegar
4 cups beef broth 
¾ cup dried green or brown lentils
1 cup frozen spinach or 1 bag fresh baby spinach 

Time: About 1 hour (30 minutes active)
Yield: about 5 cups of soup

 Slice the onions into 1/8th to 1/4th inch slices. 

Heat the oil and butter over a medium flame in a large skillet with high sides. 

Turn the heat up to medium high and add the onions. Cover and cook, for 2-3 minutes until the onions begin to brown and stick to the bottom of the pan. Pour in about 2 -4 Tbsp of water and scrape the brown bits from the bottom of the pan. Cover and cook for 2-3 more minutes and repeat the process. Continue cooking until the onions are a deep brown color, about 20-25 minutes. 

Add the thyme and salt and cook for 1 minute. 

Add the red wine vinegar and cook until evaporated, about 1-2 minutes.

Add the broth and the lentils. Bring to a boil over the highest flame. Once boiling, reduce the flame to low and simmer, covered, for about 30 minutes until the lentils are cooked, but have a little bit of crunch left to them. (Continue to cook for another 10 minutes if you prefer mushier lentils.)

Turn off the flame and stir in the spinach, either frozen or fresh, and stir to wilt. 

Test for seasoning.