Keto Cabbage Noodle Tuna Casserole

Ingredients

• 2 tbsp olive oil
• 2 tbsp grass-fed butter
• medium head green cabbage (about 1 1/2 lbs), cut into large shreds
• 1 cup onion, chopped
• 3 ribs celery, chopped
• 2 cloves garlic, minced
• sea salt
• black pepper
• 2 tsp dried dill or 2 tbsp fresh dill
• 2 tsp mustard powder
• 2 tbsp lemon zest
• juice of 1 lemon
• 1 1/2 cup heavy cream
• 1 1/4 cup Parmesan cheese, grated, divided
• 3 5oz cans albacore tuna, drained
• 1/2 cup frozen peas