Preheat the oven to 400 degrees. Remove steak from fridge to let come up to temperature.

Quarter the potatoes. Mince or grate the garlic. Halve, seed, and dice the tomato. Finely chop the parsley leaves, reserving a few for garnish.

Toss the onions and potatoes on a baking sheet with 1 tablespoon olive oil and season with salt and pepper. Roast for 25-30 minutes, tossing halfway through cooking, until soft and golden brown.

Cook the steak: heat 1 teaspoon oil in a large pan over medium-high heat. Season the steak on all sides with salt and pepper. Add the steak to the pan and cook 4-7 minutes per side, until cooked to desired doneness. Set aside to rest for 5 minutes.

Add the tomato and garlic to the pan, along with a drizzle of oil, if necessary. Reduce heat to medium and cook, tossing, for 2 minutes, until softened. Season with salt and pepper. Add the stock concentrate and 1 cup water to the pan, bring to a boil, and allow to reduce until thickened, 2-3 minutes. Remove pan from heat, then stir in 2 tablespoons butter and the chopped parsley. Taste and season with salt and pepper, if necessary.

Slice the steak against the grain and serve with the potatoes and onions. Spoon the tomato pan-sauce over the steak and garnish with the reserved parsley leaves. Enjoy!