Preheat the oven to 400 degrees and prepare a lightly greased baking dish. Thoroughly rinse produce and pat dry. Bring a medium pot of water to a boil. Finely chop onion. Finely dice celery. Finely mince garlic. Finely slice basil and parsley. Drain water from tofu, press excess water out, and whir in the food processor or bldner for a minute or so, or until slightly creamy or at the desired consistency (longer processing renders a texture closest to creamy ricotta). Halve lemon and zest one half for garnish, if desired.

In a large pan, sauté 3 minced garlic cloves and diced onion in 1 tsp. olive oil for about 5 minutes. Season with salt and pepper. Add in chopped celery stalks, half of basil, half of parsley (reserving some for garnish, if desired), and sauté for another 5 minutes. Pour processed tofu into the skillet. Stir in nutritional yeast, salt and pepper to taste, 1 Tbsp. lemon juice, and red pepper flakes to taste. Over medium heat, cook for about 8-10 minutes, or until most of the liquid cooks off. Remove from heat and set aside.

Once water is boiling, add pasta shells and cook until al dente, about 8-11 minutes. (Be careful not to overcook or break shells as you remove them from the water.) Drain shells and set aside to cool and firm a bit before stuffing.

In a medium pan, combine 3 Tbsp. olive oil, remaining parsley, remaining basil and garlic over medium-high heat. When garlic is sizzling, add canned tomatoes (with the juice from the can) and season with salt and pepper to taste. Lower the heat to medium and cook, stirring occasionally, until the liquid has evaporated and the oil begins to separate from the sauce, about 15 minutes.

Spoon about 1 cup tomato sauce into the casserole dish and spread around. Gently stuff about 2 Tbsp. tofu ricotta into each shell and place stuffed shells on top of tomato sauce. Cover shells with the remaining tomato sauce and any leftover tofu ricotta. Cover dish with tin foil and poke several air holes. Bake at 400 degrees for about 20 minutes, or until heated throughout and slightly crispy.

Place 6 stuffed shells on a plate. Ladle any remaining tomato sauce atop shells. Add any additional tofu ricotta, if desired. Garnish with remaining fresh basil, parsley, and lemon zest, if desired.