Brown the ground beef in a large skillet over medium-high heat, breaking it apart as it cooks. Drain the excess grease.
Add the red onion and sauté for a few minutes until softened.
Stir in the diced tomatoes with green chiles and corn. Cook for 2 minutes.
Reduce the heat to low. Add the Velveeta, cream cheese, pepper jack cheese, and milk. Stir constantly until the cheese is melted and the mixture is smooth.
Add more milk, 1 tablespoon at a time, if needed to reach the desired consistency.
Stir in the black beans and most of the cilantro, reserving some cilantro for topping.
Serve warm, topped with the remaining cilantro.
Notes
Cube the Velveeta into small pieces for faster, more even melting.The queso will thicken as it cools. Keep it warm over low heat, stirring occasionally, and add milk as needed to maintain desired thinness.