4-Cheese Spinach-Artichoke Dip

Melt butter in a large pot over medium heat. Add spinach, artichoke hearts, and any marinade oil that remains after chopping them. Add onion, garlic, pepper, salt, and red pepper flakes; cook, stirring regularly so it doesn't burn on the bottom, until spinach has wilted and mixture is wet, about 3 minutes.

Reduce heat to low and add cream cheese, Parmesan cheese, processed cheese, and Cheddar cheese. Stir occasionally and allow to simmer, uncovered, until cheeses have melted and some of the water from the spinach has cooked off, about 3 more minutes. This allows the herbs and spices to infuse their flavor into the dip. Serve hot.