In a saucepan, melt butter over medium heat.
Add diced onions, minced garlic, salt, cumin, granulated onion, and cayenne. Saute until onions are translucent.
Sprinkle in flour and cook, stirring continuously, for 1-2 minutes.
Pour in the can of Rotel and evaporated milk, stirring to combine.
Add shredded cheddar cheese gradually, stirring until fully melted and smooth.
Remove from heat.