Roasted Cauliflower Salad With Feta And Dates

Name: Roasted Cauliflower Salad With Feta And Dates
Ingredients: 1 large head of cauliflower (about 2½ lb.), leaves removed, stem trimmed; ¼ cup (or more) plus 2 Tbsp. extra-virgin olive oil; plus more for drizzling; 1 garlic clove, finely grated; 3 Tbsp. red wine vinegar; 2 tsp. honey; Kosher salt; 1 medium red onion, cut into 1-thick wedges through root end, layers separated; 6 oz. feta, thinly cut into slabs; 2 Tbsp. drained capers; 2 Tbsp. shelled raw pistachios; 2 big handfuls of arugula (about half of a 5-oz. package); 1 cup torn pitted Medjool dates (about 4 oz.); Freshly ground pepper