Pat the chicken breasts dry with paper towels and season with salt, pepper, and a pinch of dried oregano.

Heat 1 tablespoon of olive oil in a large skillet over medium-high heat. Sear the chicken breasts for 3-4 minutes per side, or until golden brown. Remove from skillet and set aside.

Reduce the heat to medium and add the remaining 1 tablespoon of olive oil to the skillet. Add the minced garlic and cook for 30 seconds, or until fragrant. Add the sun-dried tomatoes and cook for another minute, stirring occasionally.

Pour in the chicken broth and lemon juice, scraping up any browned bits from the bottom of the pan. Bring the sauce to a simmer and cook for 2-3 minutes, or until slightly reduced. Stir in the red pepper flakes (if using) and the remaining dried oregano.

Add the spinach to the skillet and cook until wilted, about 2-3 minutes. Stir in the feta cheese and allow it to melt slightly into the sauce.

Return the chicken breasts to the skillet and nestle them into the sauce. Spoon some of the sauce over the chicken and bring the sauce back to a simmer. Cover the skillet and cook for 5-7 minutes, or until the chicken is cooked through (internal temperature of 165°F or 74°C).

Remove from heat and let rest for a few minutes before serving. Garnish with fresh parsley or basil, if desired. Serve over pasta, rice, quinoa, or alongside a salad.