Low-Carb Tuna Casserole with Cabbage Noodles

Heat olive oil and butter in an extra large oven-proof skillet over medium heat. Add cabbage, onion, celery, garlic, salt, and pepper; saute until vegetables are crisp-tender, about 10 minutes. Mix in lemon zest, lemon juice, dill, and mustard powder.

Pour heavy cream into the pan and add 1 cup Parmesan cheese. Stir continuously until cheese has melted and combined with the cream, 3 to 4 minutes. Reduce heat to medium-low and simmer until sauce has thickened, about 10 minutes. Stir in tuna and peas and sprinkle remaining Parmesan cheese over the top of the dish.

Set an oven rack about 6 inches from the heat source and preheat the oven's broiler.

Place the skillet under the preheated broiler. Broil on high until the Parmesan on top of the casserole makes a golden brown crust, 3 to 5 minutes.