Combine olives and 1/3 cup olive oil in a blender and puree until smooth.

Add garlic, rosemary, lemon zest, and sherry vinegar to the blender and puree again.

If the black-olive oil is too thick, add more olive oil to reach desired consistency.

Preheat a grill or grill pan to high heat.

Brush radicchio quarters with 1 tablespoon olive oil and grill, turning occasionally, until wilted (about 5 minutes).

Transfer grilled radicchio to a bowl.

Toss with 2 tablespoons olive oil, shallot, and thyme, then season with salt and pepper.

Keep warm.

In a separate bowl, mix cumin, paprika, and the remaining 1 tablespoon olive oil.

Add lamb cubes to the mixture and coat evenly.

Season lamb with salt and pepper.

Grill lamb over high heat until medium-rare (about 2 minutes per side).

Transfer grilled lamb to a plate and let rest for 5 minutes.

Thread each lamb cube onto a small skewer or toothpick.

Arrange the grilled radicchio on a platter.

Top with the grilled lamb skewers.

Drizzle with the black-olive oil and serve immediately.