In a large bowl, mix the cornstarch and shredded cheese together.
Melt butter in a large pan on medium heat. Add garlic and onion, cooking until the onion is translucent (about 3 minutes).
Add the tomato and cook for another 2 minutes. Then, add the evaporated milk and cheese, stirring constantly. Once it starts to thicken up, add the spices.
Add salt to taste and the cilantro. If the dip is too thick, adjust the consistency by adding 2 tablespoons of milk. Once the texture and taste are just right, remove from heat.
Serve warm or at room temperature with tortilla chips and enjoy!