Preheat oven to 350°F (180°C).
Dice onion. In a large skillet over medium-high heat, sauté onion for about 8 minutes or until softened.
Meanwhile, mince garlic.
Add garlic, cumin, and smoked paprika to skillet. Stir and sauté 1 minute.
Reduce heat to medium-low. Add refried beans and black beans (rinsed and drained). Stir with spatula to combine. Heat for about 3 minutes until refried beans soften. Salt to taste if desired.
Transfer bean mixture to an 8 x 8 inch glass baking dish. Spread into an even layer. Then sprinkle cheese evenly on top.
Bake for 15-20 minutes or until cheese is melted.
Remove from oven. Add toppings of choice and serve with tortilla chips.