Preheat the oven to 400F. Line a baking sheet with parchment paper.
Put the portobello caps on a baking sheet gill side up, sprinkle with salt and pepper and bake for 10 minutes.
Remove the mushrooms from the oven. Crack each egg into the portobello cap and sprinkle with some more salt and pepper. If needed, adjust the portobellos by turning them or putting them right next to each other or propping them with crimped up foil so the eggs don't slide out of them.
Put portobellos with eggs in the oven and bake for 15 minutes.