Add 1 tablespoon of oil to a 10-inch cast iron skillet and heat over medium heat.
Add the sausage slices to the skillet and brown on both sides. This should take about 5-7 minutes. Transfer to a plate and set aside.
Carefully grease the bottom and sides of the skillet with the remaining 1 tablespoon of oil. Add the chopped peppers and onions and sauté for 2-3 minutes, or until they start to soften. Add in the garlic and cook for another 2 minutes, stirring frequently to ensure the garlic doesn’t burn.
Add the sausage back in and stir everything around to ensure even distribution.
In a medium-sized bowl, whisk together the eggs, salt, red pepper flakes and pepper. Pour over the sausage mixture. (You may need to reduce the heat to medium-low to ensure the frittata doesn’t burn on the bottom. You can also swirl the egg around the edges of the pan to help it seep down around the frittata and cook quicker).
Cook for 5-7 minutes, or until the eggs start to set around the edges.
Place the frittata in the oven and broil for 2-3 minutes, or until the eggs are set and the frittata is browned on top.
Remove from oven and let rest for a few minutes before cutting into slices and serving.
Store any leftovers in an airtight container in the refrigerator and enjoy within 3-4 days.
As you’re broiling the frittata in the oven at the end, make sure you’re using an oven safe skillet or pan.
This frittata has a spicy kick, so if you’re not a fan of spicy, just reduce or leave out the jalapeño pepper and crushed red pepper flakes. If you like it spicier, just add more.
The frittata will puff up a bit while it’s broiling and start to brown. Keep a close eye on it as it can start to burn quickly under the broiler.
Once removed from the oven, let the frittata sit for a few minutes before slicing and serving. The frittata will sink a bit and the edges will pull away from the sides of the skillet. That’s okay. This will make it easier to slice and lift out of the skillet without sticking.
Make sure the bottom and sides of your skillet are well oiled. This will also help prevent the frittata from sticking to your skillet.