Step 1: In a medium pot, melt the butter over medium heat.
Step 2: Add in the chopped onion, salt, pepper, thyme and lemon zest.Cook for about 3 minutes or until onions are soft.
Step 3: Add the lentils and stir to combine with other ingredients.
Step 4: Add the mushroom broth and continue to cook on medium for 5 minutes.
Step 5: Add broccoli florets. Cook for 5 more minutes.
Step 6: When the lentils and broccoli are nearly done cooking, add the spinach and cook for 1 more minute.
Step 7: Remove from the heat and pour the soup into a blender and puree on high until smooth. Serve immediately.