For the Beef Layer

1 tablespoon olive oil
1 medium yellow onion, finely diced
2 cloves garlic, minced
1 pound (450 g) ground beef (80–90% lean)
1 teaspoon salt (or to taste)
½ teaspoon black pepper
1 teaspoon smoked paprika (or regular paprika)
1 tablespoon Worcestershire sauce

For the Cheeseburger Sauce

½ cup ketchup
2 tablespoons yellow mustard
½ cup sour cream (or plain Greek yogurt)
½ cup beef broth or water
1 cup shredded cheddar cheese