Prepare the radicchio by removing any discolored outer leaves. Slice the remaining radicchio into thin strips.

Toast the bread in your oven or skillet until golden brown. Cut into bite-sized pieces once cooled.

Combine radicchio, toasted bread, and Castelvetrano olives in a large mixing bowl.

Whisk together olive oil, lemon juice, minced garlic, mayonnaise, sugar, kosher salt, and black pepper until smooth.

Drizzle the dressing over the salad and toss gently to combine.