Put a large 10- to 12-inch skillet with a lid on the stove over medium heat.

Add the olive oil to the skillet. When it looks loose and shiny, add the Italian sausage.

Cook the sausage for 5 to 6 minutes, breaking it into bite-size pieces with a wooden spoon, until it is no longer pink and browned in spots.

Use a slotted spoon to transfer the sausage to a plate. Leave the fat in the skillet.

Add the sliced onion and red bell pepper to the skillet. Add 1/2 teaspoon of the kosher salt. Cook for 5 to 6 minutes, stirring often, until the vegetables are soft and lightly golden at the edges.

Add the garlic and crushed red pepper flakes to the skillet. Stir for about 30 seconds, just until the garlic smells fragrant.

Pour the marinara sauce into the skillet. Stir well and scrape the bottom of the pan with the spoon so any browned bits mix into the sauce.

Return the cooked sausage and any juices from the plate to the skillet. Lower the heat to medium-low.

Simmer the sauce for 3 to 4 minutes, stirring once or twice, until it is slightly thicker and the sausage is heated through.

Taste the sauce and add the remaining 1/4 teaspoon kosher salt and the 1/4 teaspoon black pepper. If the sauce looks very thick, stir in 2 to 3 tablespoons of water.

Use the back of the spoon to make 4 shallow wells in the sauce so the eggs have a place to sit.

Crack 1 egg into each well in the skillet, keeping the yolks whole.