Milanesa de Res with Oaxacan Rustic Sauce

Ingredients

• 1 pound beef Skirt Steak , butterflied, cut into 4 to 6-inch pieces
• 2-1/2 teaspoons Kosher salt, divided
• 2 teaspoons ground black pepper, divided
• 1 cup all purpose flour
• 2 eggs
• 1/2 cup buttermilk
• 1/3 cup vegetable oil
• 1/2 cup shredded quesillo or mozzarella cheese
• 1/2 small white onion, thinly sliced
• 1/2 cup fresh parsley, chopped
• Cooked black beans (optional)