For the tempeh: Cut the tempeh into 1/4-inch-thick slices, about 3 inches square per slice. Combine the soy sauce, vinegar, 1/4 cup water, celery seed, chili powder, sage, thyme and onion powder in a casserole dish. Lay the tempeh slices in the dish and allow to marinate, refrigerated, for 45 minutes.
For the slaw: Finely slice the Brussels sprouts. Combine with the vegan mayonnaise, lemon juice, caraway seeds and salt and mix well. Refrigerate for at least 10 minutes.
For the tartar sauce: Combine the vegan mayonnaise, relish, ketchup, mustard and dill in a bowl and mix well. Refrigerate for at least 10 minutes.
For the dredging and breading mix: Combine the cornmeal, flour, paprika, garlic powder and celery seed in a large bowl. Mix the soy milk and lemon juice in another large bowl. Remove the tempeh from the marinade and dip each slice in the soy milk mixture, then in the breading mixture, making sure to coat all sides. Repeat with the remaining tempeh slices. Set the slices aside on a baking sheet for 10 minutes.
Heat enough olive oil to cover the bottom of a medium skillet over medium-high heat. Fry the tempeh slices in batches until golden brown on each side, 4 to 6 minutes.
Serve the tempeh with the slaw and tartar sauce.