Wash and dry all produce. Cut potatoes into cubes between 1/4 and 1/2 inch. Place in a medium, microwave-safe bowl with 1/4 cup water. Season with salt. Cover bowl with plastic wrap; poke a few holes in wrap with a fork or small knife. Microwave on high for 5 minutes. Drain well and set aside.

Quarter lime. Pat steak dry with a paper towel. Using a fork or sharp knife, poke steak all over. Season with salt and 1/4 tsp chipotle powder (we sent more; use up to 1/2 tsp if you like it spicy). Place on a plate or in a bowl. Squeeze over juice from 1 lime quarter. Set aside to marinate for about 5 minutes.

Peel and halve onion, then cut into pieces between 1/4 and 1/2 inch. Core, halve, and seed bell pepper, then cut into pieces between 1/4 and 1/2 inch. Halve tomatoes lengthwise. Trim and slice scallions. Heat a large drizzle of olive oil in a large pan over medium-high heat (use a nonstick pan if you have one).

Add potatoes, 2 tsp Southwest spice (save the rest for later), salt, and pepper to pan and toss to evenly coat. Cook without stirring until potatoes are crisp on bottom, 3-4 minutes. Toss and continue to cook until crisp all over, about 3 minutes more. Toss in onion and bell pepper and cook until tender and potatoes are done, about 3 minutes. Toss in tomatoes and half of the scallions. Season with salt and pepper. Set aside while you cook steak.

Heat a grill pan over medium-high heat. (TIP: Alternatively, heat a large pan over medium-high heat or a grill with oiled grates over direct heat.) Add steak and cook until charred on bottom, about 5 minutes. Flip and cook to desired doneness, at least 3 minutes more. Set aside off heat to rest for about 5 minutes. Stir together remaining Southwest spice, juice from 1 lime quarter, and sour cream in a small bowl, adding a small splash of water if very thick.

Divide hash between bowls or plates. Slice steak against the grain, season with salt, and arrange on top of hash. Drizzle with sour cream mixture. Sprinkle with remaining scallions. Serve with remaining lime quarters.