Leftover Meatloaf Panini with Caramelized Onions

Thinly slice sweet onions. To caramelize onions, coat a medium-sized frying with a thin even coating of olive or vegetable oil. Heat pan to medium; when oil is hot, add the onions and lower heat to a simmer. Stir occasionally for about 15 minutes and sprinkle the salt over onions evenly. Continue to cook on low for another 1/2 hour, stirring as little as possible. This is when they will start to caramelize and turn golden brown. Remove from heat and set aside.

To assemble the sandwich, lay a slice of meatloaf on each slice of bread. Top with a slice of cheese and 1/4 cup of caramelized onions. Butter the top and bottom of the bread and grill until golden brown and crunchy.