Heat the olive oil in a small skillet over medium heat. Add the peppers and onion and saute for 5-8 minutes, until softened and slightly golden.
Butter one side of each of the slices of bread. On the opposite side as the buttered side of four slices, layer each with one slice of LAND O LAKES® Deli American, ¼ of the peppers and onion mixture, ¼ of the avocado, ¼ of the salsa and sliced jalapeño, if using. Top each with another slice of LAND O LAKES® Deli American and a slice of bread.
In a hot skillet on a burner set to medium, cook each sandwich, flipping once, until golden on both sides. Slice diagonally and enjoy.
Recipe by Sarah's Cucina Bella at http://sarahscucinabella.com/2015/04/22/spicy-fajita-grilled-cheese/