Heat a large skillet over low heat. Add in butter and allow to melt. Add in the onion and salt and cook until onions are golden brown, approximately 30 minutes, stirring occasionally. Add in the lemon juice and cherries, mix to combine. Cook for 1 - 2 minutes until heated through, set aside.
Heat pork according to package directions; set aside.
Place the bread onto work surface in a single layer. Evenly spread the softened butter onto one side of each slice of bread, sprinkle with garlic powder. Turn two of the slices over and onto those slices, evenly divide the fontina cheese, pork, bleu cheese and the reserved onion/cherry mixture. Top with reserved two slices of bread, butter side up.
Heat a large skillet over low heat. Place the sandwiches into skillet and cook until golden brown, approximately 3 - 4 minutes. Flip sandwiches over and cook the second side in the same manner.