Wash and dry all produce. Peel potatoes, then cut into 3/4-inch cubes. Place in a large pot along with cauliflower and enough water to cover by 1 inch. Bring to a boil and cook until easily pierced by a knife, 12-15 minutes. Drain and return to pot.

Meanwhile, finely chop half the parsley; pick leaves from other half and reserve. Mince garlic. Halve tomatoes. Halve lemon. Heat a large pan over medium heat. Add almonds and toast, tossing frequently, until a deep gold, 4-5 minutes. Remove from pan. Finely chop once cool, leaving a few larger pieces.

In a small bowl, mix chopped parsley, almonds, a pinch of garlic, a squeeze of lemon, and 2 TBSP olive oil. Season with salt, pepper, and more lemon juice, to taste. TIP: Mixture should have a pesto-like consistency. Add another drizzle of olive oil, if needed, to loosen.

Heat a drizzle of olive oil in pan used for nuts over medium-high heat. Add tomatoes and remaining garlic. Cook, tossing, until tomatoes soften, 2-3 minutes. Season with salt and pepper. Remove from pan and cover to keep warm.

Heat a drizzle of olive oil in same pan over medium-high heat. Pat steak dry with a paper towel. Season all over with salt and pepper. Cook to desired doneness, 3-6 minutes per side. Remove from pan and let rest 5 minutes, then thinly slice against the grain.

Add sour cream, 1 TBSP butter, and 1/4 cup water to cauliflower and potatoes in pot. Place over low heat. Mash with a potato masher or fork until smooth. Season with salt and pepper. Divide mash and steak between plates. Top with tomatoes. Spoon gremolata over. Garnish with parsley leaves.