In a large pot, bring salted water to a boil over medium-high heat. Add the noodles and cook according to the package instructions until al dente. Drain.
Melt butter in a large cast iron skillet (or oven safe skillet) over medium heat. Cook onions about 2 minutes and then add in garlic. Cook until translucent. Whisk flour on top, until lightly golden.
Slowly stir in the half and half and simmer until slightly thickened, about 3-5 minutes. Remove from heat and stir in cheese. Stir until smooth.
Stir in the cooked noodles, tuna, peas, Italian seasoning, salt, and pepper until well combined.
In a small bowl, mix the panko breadcrumbs, melted butter and lemon zest. Sprinkle on top of the casserole.
Bake 20 minutes, or until bubbly. Move to the top rack or broil the last minute if you want a golden top. Garnish with chives if desired.
Notes
Vegetables: You can add in mixed vegetables, if you prefer.Tuna: I prefer the Kirkland brand. You can use two cans if you'd like extra protein (my family likes 1 best). Variation:
Feel free to make the sauce cheesier by adding 1/2 cup extra cheese to the sauce, if desired.
Use whatever cheese you like, such as sharp cheddar, pepper jack or Swiss.
I love to add fresh herbs to the sauce like thyme or parsley if I have it on hand.