Combine the dry spices: whisk together 2 teaspoons garlic powder, 1 1/2 teaspoons dried oregano, 1 teaspoon salt, 1 teaspoon dried basil, 1 teaspoon onion powder, 1/2 teaspoon cumin, 1/2 teaspoon paprika, 1/2 teaspoon pepper, and 1/2 teaspoon sugar. Set aside 2 tablespoons of this spice mix (“Reserved Spices”).
Place the remaining spice mix in a freezer-size plastic bag. Add 3 tablespoons olive oil, 1 tablespoon balsamic vinegar, and 1 tablespoon lemon juice to the bag. Whisk or massage the bag to combine, then add the 1 pound boneless skinless chicken breasts to coat. Marinate the chicken 30–60 minutes at room temperature or refrigerate up to overnight.
If the chicken was refrigerated, let it sit at room temperature 20–30 minutes before cooking.
Heat some of the listed olive oil in a Dutch oven or large ovenproof heavy pot with a tight-fitting lid until very hot. Drain the chicken from the marinade, pat the pieces dry with paper towels, and add them to the hot pot. Cook undisturbed 3–4 minutes, until the bottom is nicely browned.
Turn the chicken, cover the pot, reduce the heat to medium, and cook a further 4–6 minutes (depending on thickness) until the chicken is cooked through. Transfer the chicken to a cutting board, let rest 5 minutes, then chop into bite-size pieces. Do not clean the pot.
Preheat the oven to 400°F.
In the same pot, melt 2 tablespoons butter together with some of the listed olive oil over medium heat. Increase heat to medium-high, add 1/2 red onion (chopped), and sauté about 3 minutes, until softened.
Add 1 1/2 cups Arborio rice and cook, stirring, for 2 minutes to lightly toast the rice.
Stir in 4 1/2 cups warmed reduced-sodium chicken broth and the Reserved Spices. Bring the mixture to a boil, cover the pot, and transfer it to the preheated oven. Bake, covered, 18–20 minutes, until the rice is tender but not mushy.
Remove the pot from the oven. Stir in the remaining 1/2 cup warmed chicken broth, 1/2 cup freshly grated Parmesan cheese, and 1/4 cup feta cheese. Stir vigorously until the mixture is smooth and creamy.
Stir the chopped chicken into the risotto and heat through on the stovetop over low heat if needed. If you prefer a looser consistency, stir in additional warmed chicken broth (if available) a little at a time.
Serve topped with chopped tomatoes, chopped cucumbers, additional feta, additional freshly grated Parmesan cheese, and fresh parsley. Add a squeeze of lemon juice and season with salt and pepper to taste.