Peel onion and slice into 1/4" rounds. Trim zucchini ends and slice on an angle into 1/2" rounds. Slice Roma tomatoes into 1/2" rounds. Mince garlic. Stem, seed, and cut red bell pepper into 1/2" pieces. Trim cucumbers and cut into 1/8" dice. Zest and halve lemon. Cut one half into two wedges and juice the other half. Rinse chicken, pat dry, and season with salt and pepper.

Add tomatoes, zucchini, red bell pepper, and red onion to baking sheet. Drizzle with 2 Tbsp. olive oil, 1/2 tsp. salt, and a large pinch of pepper. Toss to coat with your hands, breaking up onion into rings as you go. Bake 25 minutes, or until vegetables are tender and lightly browned.

While vegetables cook, mix together half the lemon zest, oregano, garlic, and 1 Tbsp. olive oil in a small bowl. Place a medium oven-safe pan over medium-high heat and add 2 tsp. olive oil to hot pan. Place chicken in pan, skin side down, and immediately spoon half the oregano-garlic mixture over chicken. Cook 5-7 minutes, until skin is golden brown and crispy.

Flip and spoon remaining oregano-garlic mixture on cooked side of chicken. Place pan in oven and bake 20-25 minutes, or until chicken reaches a minimum internal temperature of 165 degrees. Once done, remove chicken from pan and rest at least 3 minutes. Be careful, handle on pan will be hot!

While chicken cooks, combine cucumber, yogurt, dill, remaining zest, and 1 Tbsp. lemon juice in a small bowl. Stir together and season with salt and pepper to taste.

Divide vegetables between two plates. Lean chicken against vegetables. Garnish each plate with lemon wedge to squeeze over dish when ready to eat. Serve tzatziki sauce on the side.