No-Soup Tuna Casserole

I'm still paying attention to the diet, but likewise, I have a serious craving for tuna casserole. To me, the brunt of what makes tuna casserole not-diet-friendly is the can of soup that's tossed in. Also, I am still using up all the eggplant I got at the farmer's market (plus I was proving to my cast iron pan I didn't forget it lives here). So I decided to try to make my own version that was a little fresher and less soupy.

Here it is. I hope you like it.

2 tablespoons vegetable oil
1 carrot, diced
1 celery stalk, diced
1/4 onion, diced
salt to taste
1 teaspoon white wine vinegar
5 cloves garlic (use less if you're not a garlic freak like I am)
4 ounces button mushrooms, cut into eighths
2 teaspoons lemon juice, divided
2 tablespoons butter
6 ounces grape tomatoes, cut in half
3 tablespoons fresh tarragon, minced
1 tablespoon fresh mint, minced

2 6-ounce (or 5-ounce, if you're buying those now) cans tuna in water
2 ears corn, kernels cut off (you're only using the kernels, reserve cob for other things)
1 12-ounce bag pasta spirals (or shape you like), cooked to package directions
1 1/2 cups sugar snap peas (or 1 cup shelled English peas)
1 ichiban eggplant, diced
1 tablespoon lemon pepper (optional)

Preheat oven to 350F. Heat oil in cast iron pan over medium heat. Add seasoned carrots and cook for 5 minutes. Add seasoned onion, cook another 5 minutes. Then toss in the seasoned celery and sprinkle in white wine vinegar, then cook that 5 more minutes. Reduce heat to low and add in garlic, mushrooms, butter and 1 teaspoon lemon. Cook it down until the mushrooms look well-softened and brown. Add in tomatoes, tarragon, mint and remaining lemon juice and cook them down another 10 or 15 minutes, stirring periodically, until a rich sauce has formed in the pan. Transfer to 2-quart casserole dish (including sauce), and add corn, peas, tuna, pasta and eggplant. If you want the lemon pepper, toss it in (I opted to just put it in my own bowl). Stir well and bake for 1 hour.