Preheat the oven to 425ºF.

Line two large baking sheets with silicone mats or parchment paper. Arrange the eggplant slices in a single layer on one of the prepared baking sheets. Bake the eggplant until soft, turning once, about 15 minutes. Remove the baking sheet from the oven and set aside to cool; then remove the eggplant from the pan.

Meanwhile, on the second prepared baking sheet, arrange the onion slices in a single layer and bake for 7 to 8 minutes. Turn over the onion slices, place the bell pepper pieces on the same baking sheet as the onion, and roast until the vegetables are tender, about 15 minutes longer. Set aside to cool.

Arrange the mushroom caps, gill side up, on the baking sheet from which the eggplant has been removed. Roast until softened, about 10 minutes.

Set aside to cool for a few minutes. Lower the oven temperature to 350ºF.

Assemble the roasted vegetables in stacks: To begin, leave the four mushroom caps, gill side up, on their baking sheet. Top each cap with a slice of eggplant, followed by a slice of onion, then a bell pepper slice, topped with a slice of tomato. Cover the baking sheet and bake until the vegetables are hot, about 20 minutes.

While the vegetables are cooking, make the sauce: In a skillet, heat 3 tablespoons of water over medium heat and add the minced onion. Cover and cook for 4 minutes, or until soft. Stir in the plum tomatoes, roasted bell peppers, miso, basil, thyme, turmeric, and black pepper to taste. Cover and cook until the vegetables are very soft, about 5 minutes longer. Transfer to a food processor and purée the sauce until smooth. Keep warm over low heat until ready to use.

When the stacks are ready, use a metal spatula to carefully remove them from the baking dish. Place one stack in the center of each of four dinner plates. Top and surround each stack with the sauce and parsley garnish, and serve hot.