Heat 1 tablespoon of the oil in a large skillet over medium-high heat. Season the steaks with 1/2 teaspoon each salt and pepper. Cook to the desired doneness, 4 to 6 minutes per side for medium-rare. Let rest 5 minutes before slicing.
Wipe out the skillet and heat the remaining 2 tablespoons of oil over medium heat. Add the fennel and 1/4 teaspoon each salt and pepper. Cook, stirring occasionally, until slightly browned and just tender, 5 to 6 minutes.
Stir in the olives and jalapeño and cook for 1 minute. Sprinkle with the fennel fronds and serve with the sliced steak.
Upgrade: Add color and a sweet shot of citrus by mixing orange segments into the sautéed fennel just before serving.