Heat the oven to 375°F. Lightly grease 8 cups of a standard muffin pan.
In a large bowl, whisk the egg with 1/4 cup of the salsa. Add the ground beef, breadcrumbs, black beans, corn, 1/4 cup of the cheddar, chili powder, cumin, garlic powder, and salt.
Mix gently with your hands or a fork just until combined. Avoid packing the mixture tightly, which can make the muffins dense.
Divide the mixture among the 8 greased muffin cups. Press it in lightly, then spoon the remaining salsa over the tops.
Bake until the muffins are cooked through, about 20 to 25 minutes. Sprinkle the remaining cheddar over them during the last 3 minutes of baking.
Let the muffins rest in the pan for 5 minutes, then lift them out carefully. Sprinkle with the chopped cilantro before serving.