Crostini with White Cheddar, Apples and Onion

I found this recipe on this website.

Ingredients

Topping
2 tablespoons olive oil
1 large yellow onion, thinly sliced
1 tablespoon balsamic or apple cider vinegar
1/2 teaspoon salt
2 Gala or Golden Delicious apples, peeled, cored, and thinly sliced
1/3 cup brown sugar
1/4 teaspoon cinnamon
non-stick cooking spray

24, 1/2-inch-thick slices of whole-wheat baguette, cut on the diagonal
1 8-ounce package reduced- fat Cabot white cheddar cheese, cut into 24 slices
1 teaspoon fresh thyme leaves, chopped

Directions
Warm half the oil in a large, deep skillet over medium-high heat. Add the onion, salt, and vinegar. Cook 15-20 minutes, stirring occasionally, until onions are golden brown. Add 1-2 tablespoons of water as the onions cook if they begin to burn or stick.

Meanwhile, in a large bowl, combine apples, sugar, and cinnamon. Toss to coat. Coat a large skillet with cooking spray and warm over medium heat. Add the apples and remaining olive oil to the skillet with the onions and cook for an additional 10-12 minutes, stirring frequently, until the apples soften but do not become mushy.

Preheat oven 400° F. Cover two large cookies sheets with parchment paper or aluminum foil. Arrange the bread slices and distribute the onion and apple mixture evenly over the bread slices. Top with cheese slices. Bake for 8-10 minutes or until cheese melts. Transfer to a large platter and garnish with fresh thyme.