Preheat the oven to 300 degrees and line a baking sheet with parchment paper.
Remove the ends from the zucchini. Slice it into 8 equal rounds, each one about ¾”-inch thick.
Slice off the ends of the red onion. Very carefully, and with the skin intact, slice it into 4 equal rounds, each one about ½”-inch thick.
In a small bowl, stir together the olive oil, dried basil, salt, and pepper. Using a pastry brush, brush both sides of each eggplant and onion round, and place them on the baking sheet. If you don’t have a pastry brush, your hands will work just fine!
Bake the zucchini and onion for 45 minutes. Flip everything over, brush with more oil if they seem dry, and bake for another 15 minutes. By this time, the zucchini should be a nice golden color and feel soft if you press gently in the center. The onion will have a golden brown color and a deep, delicious aroma.
Remove the dried onion skins and any outer layers that have dried out. Immediately drizzle with red wine vinegar and sprinkle with Aleppo chili flakes. Allow to cool slightly before handling.
To serve, stack two zucchini slices on a plate with one onion slice on top. Sprinkle with whole mint leaves and extra chili if you like a little extra heat.