Pat chicken pieces dry with paper towels and season with salt and pepper. Heat olive oil in a large Dutch oven or deep skillet over medium-high heat until shimmering, approximately 2 minutes. Working in batches, sear chicken until golden brown on both sides, about 3-4 minutes per side, then set aside.
In the same pot, add diced onion and sauté for 2 minutes until softened. Stir in minced garlic and cook for 30 seconds until fragrant. Pour in chicken broth and fresh lemon juice, scraping the bottom to release browned bits.
Return chicken to the pot and add halved baby potatoes, lemon zest, oregano, and thyme. Bring to a simmer, reduce heat to medium, and cover partially. Cook for 12-15 minutes until potatoes are tender and chicken reaches an internal temperature of 165°F.
The one pot lemon chicken recipe comes together perfectly when you stir in baby spinach and butter. Cook uncovered for 2-3 minutes until spinach wilts completely. Taste and adjust seasonings as needed because individual salt preferences vary.
Transfer to serving bowls and garnish generously with fresh chopped parsley. Drizzle any cooking liquid over each portion to keep the bright one pot chicken moist and flavorful.