Warm a small pan over medium heat. Drizzle with olive oil and add kale and minced garlic. Sauté for 1-2 minutes until kale is wilted. Add in the roasted cherry tomatoes to combine. Sauté for one more minute.
Preheat the oven to 400°F. Spray an oven-safe skillet with cooking spray. Add the roasted tomatoes, kale, ¾ of the feta (reserve a couple tablespoons to sprinkle on top), and the basil.
In a large bowl, whisk together the 8 eggs, heavy cream, and sea salt. Pour the egg mixture over the vegetables.
Bake for 20-25 minutes until the eggs are set. Remove from the oven and sprinkle the reserved feta cheese on top. Let the frittata cool for 5 minutes.
Slice into 6 pieces and serve with a drizzle of balsamic glaze and additional basil.