Asparagus Frittata

Ingredients (serves 4): 2 tablespoons unsalted butter 1/3 cup diced onions 1/2 teaspoon salt 500g asparagus, tough ends snapped off, spears cut diagonally into 25mm lengths 6 large eggs, lightly beaten 1 cup shredded cheddar cheese   Method: Heat butter into a 10-inch oven-proof frying pan over medium-high heat. Add onions and cook, stirring occasionally, until…