Milanesa De Res with Oaxacan Rustic Sauce

Ingredients

• 1 pound Beef Skirt Steak, butterflied, cut into 4 to 6-inch pieces
• 2-1/2 teaspoon 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)
• 2 cups Panko bread crumbs
• 1/2 cup finely grated Parmesan cheese
• 1/2 cup finely grated Pecorino Romano cheese
• 1/2 cup fresh parsley, finely chopped
• Grated peel of 1 lemon
• Grated peel of 1 orange
• 6 medium ripe tomatoes
• 2 serrano chiles, stemmed
• 1/2 small white onion + 1/4 cup thinly sliced onion
• 1 cup water
• 1 sprig fresh epazote
• 1/2 tsp Kosher salt
• 1 tablespoon vegetable oil