How to Make It
Preheat oven to broil with oven rack 6 to 8 inches from heat. Heat oil in a large ovenproof skillet over medium-high. Add onion and garlic; cook, stirring often, until softened, about 5 minutes. Add oregano, salt, black pepper, and crushed red pepper, if using. Cook, stirring, for 1 minute. Stir in beans.
Add tomatoes, crushing them lightly with your hands, and their juices. Stir to combine. Bring to a simmer and cook, stirring occasionally, until liquid is slightly reduced, about 5 minutes.
Top mixture with cheese and transfer skillet to oven. Broil until cheese is melted, bubbly, and browned in spots, 3 to 4 minutes. Serve with crusty bread or toast.