Smoked Gouda and Caramelized Onion Quesadillas

My friend, Jamie, brought Smoked Gouda and Caramelized Onion Quesadillas as an appetizer to a dinner party awhile back. She thought they were just ok, but I thought they were excellent. I liked the combination of the sweet onions, salty prosciutto, and the smoky Gouda. Even though they are considered an appetizer, I make them for myself every so often, one or two at a time. I just refrigerate the caramelized onions that I don't use in the first batch. They are great with a soup or a salad. This is what I ate last night, when the rest of the family was eaten Kid Cuisines and frozen pizza.

SMOKED GOUDA AND CARAMELIZED ONION QUESADILLAS
(from Epicurious.com -- one of my favorite sources of online recipes)

2 tablespoons (1/4 stick) butter (I use 1 tablespoon butter and 1 tablespoon oil)
1 large onion, thinly sliced (I usually use two, but I love caramelized onions)
1 tablespoon golden brown sugar
1/4 teaspoon white wine vinegar

1 1/2 cups grated smoked Gouda cheese
4 10-inch-diameter flour tortillas (I usually use smaller ones)
2 ounces sliced prosciutto, chopped
2 tablespoons (1/4 stick) butter, melted

Melt 2 tablespoons butter in heavy medium skillet over medium heat. Add onion, brown sugar and vinegar; sauté until onion is golden brown, stirring frequently, about 25 minutes. Remove from heat. Cool to room temperature.

Preheat oven to 350°F. Sprinkle cheese over half of each tortilla, dividing equally. Sprinkle prosciutto and sautéed onion over cheese. Season with pepper. Fold other half of each tortilla over cheese mixture. Brush tortilla with some of melted butter.

Brush heavy large skillet with some of melted butter (I brush the tortillas, not the skillet). Place over medium-high heat. Working in batches, cook quesadillas just until brown spots appear, brushing skillet with butter between batches, about 2 minutes per side. Transfer quesadillas to heavy large baking sheet.

Bake until tortillas are golden and cheese melts, about 5 minutes. (If the cheese melts when you cook them in the pan, which it sometimes does, this step is unnecessary.)

Transfer quesadillas to work surface. Cut each into 6 triangles. Arrange on platter and serve hot.