Fry bacon over medium heat until crisp. Remove and drain on paper towels, then
crumble. Pour off and discard all but 1 1/2 teaspoons bacon drippings. Place pan over medium heat. Add onions;
saute,
stirring, until softened, 2-3 minutes. Add tomatoes, vinegar and red pepper flakes; cook and
stir only 30 seconds more. Do not over cook tomatoes. Remove from heat. Season generously with salt. Place tortillas on work surface. Spread each with 2 tablespoons goat cheese. Divide
crumbled bacon and sprinkle over half of each tortilla. Divide and spread tomato
mixture over bacon. Place 3-4 stemmed, cleaned, and dried watercress sprigs or 2-3 arugula leaves over tomatoes on each tortilla.
Fold tortillas in half. (Quesadillas can be assembled 30 minutes ahead and held at
cool room temperature. Keep loosely covered with plastic wrap.) When ready to cook quesadillas, heat stove-top grill pan or medium-large skillet over medium-high heat; brush lightly with olive oil. When oil is hot, add enough quesadillas to fit comfortably in single layer.
Grill or
saute until lightly
browned, about 2 minutes per side. Remove and continue, adding more oil if needed, until all quesadillas are cooked.
