Preheat oven to 425 F. Line sheet pan with parchment paper.
For potatoes, in large bowl, toss together all ingredients, transfer to parchment-lined sheet pan, and bake until tender, golden brown, and crispy, 30 to 35 minutes, tossing after about 20 minutes.
Meanwhile, prepare sauce. In small bowl, stir together parsley, basil, oregano, garlic, 2 Tbsp of oil, lemon zest, lemon juice, red pepper flakes, and 1/4 tsp of salt, or to taste, then set aside.
When potatoes have about 8 minutes left, prepare tenderloin steaks. Use 1 tsp of oil to coat the steaks, then sprinkle meat with 1/4 tsp salt each, or to taste, and pepper.
In large oven-proof skillet, heat remaining 2 tsp of oil over medium high heat. Add steaks and cook for 3 minutes on each side for medium rare, 130 F on a meat thermometer (or less or more, as desired).Allow to rest while potatoes finish roasting. Transfer to four plates or a platter and serve with potatoes and sauce. If you don’t want to turn on the oven, you can also roast potatoes using an air fryer at 350 F for 15 minutes, tossing halfway through cooking.