Arrange the pierogies in an 11 x 7-inch glass baking dish coated with cooking spray. Cook bacon in a saucepan over medium heat until crisp; remove from pan. Set aside. Carmelize onions by cooking them over low heat and covered, in 3 Tbsp of olive oil, stirring occasionally. Should take about 15 mins.
Meanwhile add garlic to “bacon drippings” in pan, and cook for 30 seconds, stirring constantly. Add 1/3 cup cream cheese to pan, and cook for 1 minute or until cream cheese begins to melt, stirring frequently. Gradually add vegetable broth to pan, stirring with a whisk until smooth.
Distribute carmelized onions over pierogis.
Pour the cream cheese mixture evenly over pierogies. Top evenly with 1/2 cup cheddar cheese.
Bake at 400° for 20 minutes or until bubbly and thoroughly heated. Remove from oven, and sprinkle with bacon, tomato, and pepper.