Heat oven to 425°F and arrange rack in the upper third of your oven.
Heat 3 tablespoons olive oil in a large non-stick, oven-safe frying pan over medium-high heat. Add 1/2 diced onion and 8 ounces quartered mushrooms and cook, stirring occasionally, until browned, about 5 minutes.
Reduce heat to medium, add 3 sliced jalapeños and 2 chopped garlic cloves and cook 1 minute more. Add 2 pounds chopped tomatoes and season generously with salt. Bring to a heavy simmer and cook until tomatoes have broken down and sauce has thickened, about 20 minutes.
Remove from heat and taste sauce, adding more salt, if necessary. Make 4-6 wells in the tomato sauce (depending on how many eggs you're using) and crack 1 egg into each well. Transfer pan to the top of the oven and bake until eggs are the desired doneness; about 5 minutes for soft set, or longer if you want the yolks more done. Sprinkle with scallions and serve with toast or warm tortillas.