Beef Tartare with Smoked Cheddar

• 1 shallot, thinly sliced
• 2 tablespoons red wine vinegar
• 1 teaspoon sugar
• ½ teaspoon kosher salt, plus more
• ½ pound lean top sirloin, preferably grass-fed
• 4 teaspoons buckwheat groats
• 1 1-inch piece horseradish, peeled, finely grated
• ¼ cup finely grated smoked cheddar
• 4 Brazil nuts or 8 raw almonds, finely grated

Olive oil (for serving)

1. Combine shallot, vinegar, sugar, and ½ tsp. salt in a small bowl. Let sit 30 minutes for shallot to soften.
2. Chill beef in freezer 15 minutes; cut into ¼" cubes. Mix beef, shallots, and 2 tsp. shallot pickling liquid to evenly distribute shallots; season with salt.
3. While beef is chilling, toast groats in a dry medium skillet over medium heat, tossing constantly, until just fragrant, about 2 minutes. Transfer to a plate.
4. Divide tartare among chilled plates and top with horseradish, cheddar, Brazil nuts, and groats. Drizzle with oil.