For Sunny-Side Up, Over-Easy or Over-Hard Eggs: Heat half of the butter in large nonstick skillet set over medium-high heat until just melted. Break 4 eggs and slip into skillet 1 at a time. Immediately reduce heat to low.
Cook eggs for about 5 minutes or until whites are completely set and yolks begin to thicken but are not hard. Serve as is or flip eggs over carefully and cook to desired doneness. Sprinkle eggs lightly with salt and pepper. (Repeat with remaining butter and eggs, or prepare all 8 eggs at once in 2 large nonstick skillets or on one large flat griddle.)
Spread warm refried beans evenly over tortillas. Spoon tomatillo salsa over half the tortillas and tomato salsa over remaining tortillas. Top each tortilla with 1 fried egg. Transfer one of each salsa-topped tortillas to 4 dinner plates and garnish with red onion and cilantro. Serve immediately.
Tip: Mix 1/4 cup regular sour cream or light sour cream with 1 tbsp. fresh lime juice for drizzling over eggs. Or garnish with chopped avocado and lime wedges.
Tip: Prepare recipe with refried black beans instead of the pinto beans if desired.