Preheat oven to 325 degrees.
Brush one side of each bread slice with olive oil and place on baking sheet. Bake until lightly toasted, 3-5 minutes. Remove from oven and let cool.
Heat remaining 3 Tbsp of oil in a large skillet over medium heat.
Add onion and saute until softened; about 5 minutes.
Add garlic and red pepper flakes and cook for an additional minute.
Add half of the kale and cook for 2-3 minutes or until it begins to wilt.
Add remaining kale and saute for an additional 5-8 minutes or until lightly wilted.
Season with salt and pepper.
Spoon kale mixture on top of bread slices.
Top with grated Parmesan cheese.