In a bowl whisk together garlic powder, dried oregano, salt, dried basil, onion powder, cumin, paprika, black pepper, and sugar to make the spice mix; set aside 2 tablespoons of this mixture for cooking.
In a freezer-size plastic bag combine the reserved 2 tablespoons spice mix with 3 tablespoons olive oil, 1 tablespoon balsamic vinegar, and 1 tablespoon lemon juice; add the chicken, seal, and marinate 30–60 minutes at room temperature or refrigerate up to overnight.
If refrigerated, let the marinated chicken sit at room temperature 20–30 minutes before cooking. Heat 1 tablespoon olive oil in a Dutch oven or large ovenproof heavy pot over medium-high heat.
Drain chicken from the marinade, pat dry, then add to the hot pot. Cook undisturbed 3–4 minutes until browned, turn, cover, reduce heat to medium and cook 4–6 more minutes or until cooked through. Transfer to a cutting board and rest 5 minutes, then chop into bite-size pieces. Do not clean the pot.
Preheat the oven to 400°F (200°C).
In the same pot, melt 2 tablespoons butter with 1 tablespoon olive oil over medium heat. Increase to medium-high and sauté the chopped red onion about 3 minutes until softened.
Add the Arborio rice and cook, stirring, for 2 minutes to toast the grains.
Stir in 4 1/2 cups warm chicken broth and the reserved spice mix. Bring to a boil, cover, and transfer the covered pot to the preheated oven. Bake 18–20 minutes, until the rice is tender but not mushy.
Remove the pot from the oven and stir in the remaining 1/2 cup chicken broth, 1/2 cup Parmesan, and 1/4 cup feta. Stir vigorously until smooth, then fold in the chopped chicken and heat through; add extra broth for a looser risotto if desired.
Garnish with chopped tomatoes, additional feta, extra freshly grated Parmesan, chopped cucumbers, parsley, and a squeeze of lemon juice. Season with salt and pepper to taste and serve.
