Cauliflower Bolognese

Name: Cauliflower Bolognese
Ingredients: 12 oz. mushrooms, such as shiitake or crimini, stems removed; 1 medium head of cauliflower (about 2¼ lb.), broken into florets; ¼ cup plus 2 Tbsp. extra-virgin olive oil, plus more for drizzling; 4 Tbsp. unsalted butter, divided; 1 large onion, finely chopped; 6 garlic cloves, thinly sliced; 1 chile, such as serrano, Holland, or Fresno, thinly sliced, or ½ tsp. crushed red pepper flakes; 1 Tbsp. finely chopped rosemary; ⅓ cup double-concentrated tomato paste; Kosher salt; 1 lb. rigatoni; 2 oz. finely grated Parmesan (about 1 cup), plus more for serving; 3 Tbsp. finely chopped parsley; ½ lemon