Score flesh of zucchini and eggplant in a crosshatch pattern, and place halves, cut side down, on paper towel or a clean tea towel and let sweat, 10 minutes.
In a bowl, stir together the syrup, vinegar, and hot sauce until smooth; set aside.
Transfer zucchini, eggplant, and onions to a large plate or sheet pan, brush with oil, then glaze liberally with syrup mixture.
Put zucchini and eggplant on grill, cut side down. Grill until slightly charred, 3-4 minutes. Add glazed onions and lemon halves, cut side down, to grill. Flip zucchini and eggplant, baste again, close lid, and cook another 3 minutes. Remove everything to a platter, squeeze grilled lemon overtop, and drizzle on any remaining glaze. Dress with parsley and basil leaves to finish.
Notes
This recipe was originally published in the June/July 2020 issue of Cottage Life.Want more vegetarian grill recipes? Try our Buffalo Cauliflower or Pulled Jackfruit Tacos.