Heat butter in a pot over medium heat.
Add green chilies and tomatoes. Stir for one minute.
Pour in heavy cream and milk. Stir well.
Mix cornstarch with a little milk. Stir into the pot.
Add shredded cheddar and Monterey Jack cheese.
Stir until the cheese melts fully.
Add salt, black pepper, garlic powder, and onion powder, then stir.
Stir until the dip gets thick.
Add cayenne pepper for extra spice if you want.
Remove from the stove and allow it to cool briefly.
Serve warm with chips or as a topping.