Season seitan slices with parsley, 1/2 of the lemon juice, garlic powder, salt, and black pepper. Fold each slice in half, seasoned-side facing inwards, and place in a 9x13-inch baking dish.
Sprinkle remaining lemon juice over artichoke hearts; spread artichokes out between seitan slices.
Stir spicy tomato sauce and wine together in a bowl; pour over seitan and artichokes. Toss croutons and olive oil together in another bowl. Spread croutons and mozzarella cheese over tomato sauce.
Bake in the preheated oven until golden brown and bubbly, 30 to 40 minutes.
