Preheat oven to 375 degrees.
Lightly spray a 9x13 baking dish with cooking spray and arrange the frozen pierogi in a single layer. You may have some overlap and that is just fine.
Slice the bacon into ½-3/4 inch pieces. In a rimmed skillet, cook bacon over medium heat until crisp. Leaving dripping in the pan, transfer to a plate, and set aside.
Add garlic to drippings in pan, and cook for 30 seconds, stirring constantly. Add cream cheese to pan, whisk and cook for 1 minute or until cream cheese begins to melt. Add the chicken broth and pepper to pan and whisk until smooth.
Pour the cream cheese mixture evenly over pierogis. Top with cheese and then the bacon.
Bake uncovered for 30 minutes. Remove from oven and top with tomatoes and green onions. Serve immediately.