Heat the olive oil in a large pot over medium heat. Add the diced onion and cook for 5 minutes until softened.
Stir in the minced garlic and cook for 1 minute more.
Add the berbere spice and tomato paste. Stir for 30 seconds to toast the spices.
Pour in the vegetable broth and add the rinsed lentils. Bring to a boil, then reduce to a simmer.
Cover and cook for 20 minutes, stirring occasionally.
Stir in the chopped collard greens and continue simmering uncovered for 15 minutes until the lentils are tender and the greens are wilted.
Season with salt to taste. Serve with lemon wedges on the side.