Drizzle the steak with vegetable oil and very liberally, season the steak with salt and pepper, to taste. Let the steak sit out at room temperature for 30 to 60 minutes.
Preheat the oven to 400 degrees F and heat the grill to hot.
In a small bowl, mix together the garlic, olive oil, and a generous pinch of salt and pepper. Lay the potatoes on a baking sheet and toss with the garlic-infused oil. Roast the potatoes for 18 minutes, or until deep golden, turning halfway through. Set the potatoes aside.
Place the seasoned steak on the hot grill and grill the steak until an instant-read thermometer reads 125 degrees F for medium-rare, about 3 minutes per side. Remove the steak from the grill and let rest under tented foil.
To assemble the salad: Divide the lettuce among 4 plates. Sprinkle on the halved tomatoes. Divide the warm potatoes among the plates. Drizzle with the Sour Cream-Bacon Dressing. Slice the steak thinly on the bias and fan on top. Top the salad with the shredded Cheddar cheese.
Sour Cream-Bacon Dressing:
In a small bowl, whisk together the mustard, vinegar, sour cream, and garlic powder. Drizzle in the oil and bacon fat to emulsify. Whisk in the chopped bacon, green onions, and season with salt, and pepper, to taste, if necessary.