Preheat the oven to 375°F.
Halve the avocados and remove the pits. Scoop out 1-2 tablespoons of flesh from each half to make an egg-sized cavity. Brush the cut surfaces with lime or lemon juice if using.
Arrange the halves in a baking dish, wedging crumpled foil around any that tip.
Crack one egg into a small cup, then pour it slowly into each cavity, stopping before it reaches the rim. Season with salt and pepper.
Bake for 15-18 minutes, until the whites are opaque and the yolk is firm. Insert a food thermometer into the center of the egg; for a fully safe egg dish, it should read 160°F. If lower, bake 2 more minutes and recheck.
Air fryer variation: cook at 375°F, start checking around 8 minutes and continue until the egg reaches 160°F. Timing varies by appliance.
Cool for 2 minutes, add toppings and serve.