Prep the Veggies: Preheat your oven to 450°F / 230°C.
Line a large baking sheet with parchment paper. Halve the plum tomatoes lengthwise, scooping out the seeds and ribs but leaving the stems intact.
In the cavity of each tomato half, sprinkle a pinch of sugar, a pinch of salt, and a few drops of balsamic vinegar.
Drizzle ½ teaspoon of olive oil over each half.
Roast the Veggies: Slice the eggplant into 12 rounds.
Brush both sides of each slice with olive oil and arrange them on the baking sheet with the tomatoes.
Season the eggplant with a little salt, if you like.
Roast for 15 minutes. Carefully flip the eggplant slices and roast for another 15 minutes, until the eggplant is tender and browned and the tomatoes are beautifully wrinkled.
Let the veggies cool on the pan for 10 minutes.
Reduce the oven temperature to 350°F / 175°C.
Cook the Amaranth: While the veggies roast, bring 1 cup (240 ml) of water to a boil in a small saucepan.
Stir in the amaranth, reduce the heat to a medium-low simmer, cover, and cook for 20 minutes, or until all the water is absorbed.
Let it stand for 5 minutes, then fluff with a fork.
Transfer the cooked amaranth to a bowl and stir in ¼ cup of the basil pesto. Assemble and Bake: Line a clean baking sheet with parchment paper and brush it lightly with oil.
Arrange the roasted tomato halves on the sheet. Spoon about 1 tablespoon (15 ml / 0.5 fl oz) of the pesto amaranth mixture into each tomato cavity.
Top each one with a slice of roasted eggplant, a slice of fresh mozzarella, and a small dab of the remaining pesto. You might have some extra amaranth mixture, which is delicious on its own!
Bake for 6 to 8 minutes, just until everything is warmed through and the cheese is melty.
Don't Waste the Extras: Any leftover pesto amaranth is fantastic as a side dish for another meal, stirred into a soup for extra body, or enjoyed cold as a salad.
