(Nutrition information is calculated using an ingredient database and should be considered an estimate.)
Preheat oven to 375 degrees F.
Place 2 tablespoons Country Crock® original spread in a microwave safe bowl and microwave for 30 seconds, or until melted.
In a large bowl, add the eggs, milk, mozzarella shreds, and 1/4 teaspoon of kosher salt and whisk well to combine. Add the melted Country Crock® to the bowl and whisk quickly to incorporate. Set mixture aside.
Melt the remaining 2 tablespoons of Country Crock® in a large cast iron skillet set over medium heat. Add the onions and sauté until soft, about 5 minutes. Add the bell pepper and asparagus to the skillet and sauté for 3 to 5 more minutes, or until the vegetables are cooked through.
Reduce the heat to low and pour the egg mixture into the skillet. Cook for 3 to 4 minutes on the stovetop to create a bottom crust on the frittata.
Transfer the frittata to the oven and bake for 20 to 25 minutes, or until set all the way through and the top is golden brown Let the frittata cool for 10 minutes before serving. The frittata is delicious warm or at room temperature.