Set a 10-inch skillet with a lid on the stove over medium heat. Add the butter to the skillet.

When the butter has melted, add the chopped onion to the skillet.

Cook the onion for 4 to 5 minutes, stirring now and then, until it is soft and starting to turn light gold at the edges.

Add half of the spinach to the skillet. Stir until it starts to shrink down.

Add the remaining spinach to the skillet. Cook for 1 to 2 minutes, stirring, until all of the spinach is wilted.

Spoon both cans of baked beans, including their sauce, into the skillet.

Stir the beans with the onion and spinach until everything is evenly mixed. Add the black pepper.

Let the bean mixture come to a gentle simmer, with small bubbles around the edges. If it looks very thick, stir in 2 tablespoons of water to loosen it slightly.

Turn the heat down to low. Use the back of a spoon to make 4 shallow spaces in the bean mixture.

Crack 1 egg into a small bowl, then slide it into one of the spaces in the skillet. Repeat with the remaining eggs so the eggs stay separate and the yolks stay whole.

Sprinkle the shredded cheddar over the beans around the eggs, leaving the yolks mostly uncovered.

Cover the skillet with the lid. Cook for 5 to 8 minutes, until the egg whites look set and opaque. For firmer yolks, cook 1 to 2 minutes longer.