Nutrition information per burger (with bun): 448 calories; 23.5 g fat; 8.7 g saturated fat; 90.4 mg cholesterol; 360.6 mg sodium; 24.4 g carbohydrate; 3.3 g fiber; 0.5 g sugar; 33.6 g protein
Warm cast iron skillet in the oven while it preheats to 425°F.
Meanwhile, season ground beef with salt and pepper, as desired, and form into four burger patties.
Once the skillet is hot, remove it from the oven using oven mitts. Add oil to skillet.
Add burgers then place skillet back in the oven and bake for 8–10 minutes for medium-rare, 11–12 minutes for medium or 13–15 minutes for medium-well.
Top burgers with sliced avocado and Swiss cheese.