Preheat the oven to 400°F (200°C).
Cut the eggplant into long wedges, about 1/2" (2 cm) at the widest part. Then, cut across, but not through, the wedges in a series of shallow cuts about 1/2" (2 cm) apart. Put eggplant in a roasting dish.
Separate 1 tbsp per serving of yogurt into a small bowl. Add the harissa and 1/2 of the oil. Mix and brush over eggplant.
Slice the red pepper and put it into the baking dish and drizzle over the remaining 1/2 of oil.
Season with salt and pepper and bake for 20-25 minutes until the eggplant is lightly browned and cooked through.
Meanwhile, cook the onion in a frying pan over medium heat for at least 10-15 minutes to caramelize. Stir frequently and season to taste while the onion cooks. Remove from heat when browned and crisped.
While everything is cooking, mash the rest of the yogurt and the feta cheese together with a fork to make the feta cream.
On each plate, create a base of the feta cream, then portion out the roasted veggies. Top with optional fresh herbs.