Cost per Serving:
1. Preheat oven to 400°F. Mix beans with lemon juice and olive oil in a large bowl. Use a fork to lightly mash; season with salt and pepper.
2. Place tortillas on a large rimmed baking sheet. Divide beans evenly among tortillas and spread. Top with equal amounts of cheese and salsa. Bake until cheese begins to melt, about 10 minutes.
3. Melt butter in a large nonstick skillet over medium heat. Break eggs into skillet; season with salt and pepper. Cook until whites are firm and yolks are beginning to set, 5 to 7 minutes.
4. Remove tortillas from oven. Top each with 1 egg, being careful to not break yolks. Return to oven and bake until warmed through and eggs are set, 3 to 5 minutes. Serve warm topped with avocado and sour cream, if desired.