Cauliflower Steaks and Purée with Walnut-Caper Salsa

Name: Cauliflower Steaks and Purée with Walnut-Caper Salsa
Ingredients: ⅓ cup walnuts; ¼ cup olive oil; 2 tablespoons drained capers, patted dry; 1 Fresno chile, seeds removed, finely chopped; 3 tablespoons coarsely chopped parsley; 1 tablespoon dried currants; 1 tablespoon sherry vinegar or red wine vinegar; 1 teaspoon finely grated lemon zest; Kosher salt; 1 small head of cauliflower; Kosher salt; 1 garlic clove, finely grated; 2 tablespoons fresh lemon juice; 2 tablespoons tahini; 2 tablespoons olive oil; 1 tablespoon unsalted butter; 2 sprigs oregano; 2 3-inch strips lemon zest; Lemon wedges (for serving)