recipe for queso dip

Ingredients 2 tablespoons unsalted butter 1 small onion, finely chopped 2 cloves garlic, minced 1 jalapeño, finely chopped (seeds removed for less heat) 2 tablespoons all-purpose flour 1 cup whole milk 1 cup heavy cream 2 cups shredded cheddar cheese 1 cup shredded Monterey Jack cheese 1 can (10 oz) diced tomatoes and green chilies, drained (like Rotel)