Chop cauliflower into florets and steam in the microwave for 4 minutes, until fork tender. Remove from microwave, drain water, and set aside.
For the Tofu
If using water packed tofu, press between 2 heavy plates wrapped in paper towels to absorb moisture.
Crumble drained and pressed tofu into a large bowl and mix with lemon juice, nutritional yeast flakes, salt, pepper, italian seasoning, stirring to combine.
For the Red Sauce
In a large saucepan over medium high heat, saute dried spices and garlic in olive oil for 2-3 minutes. Add blended tomatoes and simmer for 10 minutes.
For the White Sauce
In another large saucepan, melt vegan butter until bubbly. Whisk in flour and cook for 1 minute.
Add tahini, lemon juice, and almond milk, whisking constantly until flour mixture is smooth. Pour over top of steamed cauliflower and toss to coat. Set aside.
Assemble the Casserole
Preheat oven to 400 degrees F.
Press tofu mixture in bottom of 9 x 9 square glass baking dish. Top with cauliflower mixture, then top with tomato sauce.
Bake casserole for 30 minutes, or until casserole is bubbly around the edges and the center is hot.
Remove from oven and let sit at least 15 minutes to set.