Heat olive oil in a large pot over medium heat. Add diced onion, minced garlic, carrots, and celery, stirring frequently until the vegetables are softened and fragrant, about five to seven minutes.

Pour in the vegetable broth and add the dried green lentils, stirring to combine evenly. Bring the mixture to a boil, then immediately reduce heat to medium-low.

Add the canned diced tomatoes with their juices, bay leaf, oregano, thyme, and cumin to create a heartwarming lentil dinner base. Simmer for twenty to twenty-five minutes until lentils are tender but not falling apart.

Stir in fresh spinach and lemon juice, allowing the spinach to wilt completely into the cozy summer lentil soup dinner recipe, about two to three minutes.

Taste and adjust seasoning with salt and pepper as needed. Remove the bay leaf before serving your warm summer soup.