Preheat oven to 300°. Melt butter with 3 TBS oil, stirring over low heat. Arrange bread slices on baking sheet and brush both sides of bread with butter mixture. Bake until crisp and golden, turning once (about 10-15 minutes).
Heat remaining 3 TBS oil in large skillet. Add onions and cook over low heat until soft. Add garlic and cook an additional minute. Add tomatoes and pepper flakes. Cook over medium heat until liquid evaporates (10-15 minutes), stirring frequently. Stir in one half of chopped basil at end of cooking time.
Preheat oven to 350°. Spread toasted bread slices with tomato mixture. Top with crumbled bacon. Place on baking sheet and heat through (approximately 8-10 minutes). Remove to platter and garnish with remaining basil. Appetizer serving for 8.