Preheat the oven to 350°F. Have ready a sheet of aluminum foil at least 16 inches long.

In a food processor, pulse the garlic. Add the lentils, sundried tomatoes, broth, tamari, and olive oil and puree until relatively smooth.

In a large mixing bowl, mix the wheat gluten, nutritional yeast, paprika, thyme, and a few grinds of black pepper. Make a well in the center and add the lentil mixture. Stir with a wooden spoon until the mixture starts coming together to form a ball of dough. Knead until everything is well incorporated.

Shape the seitan into a log about 8 inches long. It doesn’t need to be perfect; it will adjust as it bakes. Place the log lengthwise in the center of the foil and roll it up like a Tootsie Roll, making sure the ends are tightly wrapped. Place the log on a baking sheet and bake for 1 hour 15 minutes, turning the roll every 20 minutes for even cooking.

Preheat a 4-quart pot over medium heat. Heat the oil, then sauté the onion with a pinch of salt until lightly caramelized, about 5 minutes. Add the garlic and rosemary and sauté until fragrant, about 30 seconds.

Mix in the tomatoes to deglaze the pan. Add the potatoes, carrots, celery, broth, remaining 1 teaspoon salt, and a few grinds of black pepper. Cover and bring to a boil. Once boiling, lower the heat and simmer, covered, until the potatoes are tender, about 15 minutes. Lower the heat to the lowest setting and cook, covered, for 20 more minutes to develop the flavors.

Once the seitan roast is cooked through, let it cool until not too hot to handle. Unwrap the foil and place the roast right into the stew. Let it soak for about 10 minutes with the heat turned off.

Remove the roast from the stew, place it on a cutting board, and cut into 1/4-inch-thick slices. Transfer the stew to a casserole dish and place the sliced roast on top. Serve.