Preheat the oven to 375ºF.

Prepare the spice rub. Add the garlic powder, salt, and pepper to a small bowl. Mix with a spoon and set aside.

Place the chicken breasts onto a cutting board and slice the chicken in half lengthwise with a sharp knife leaving the chicken breast tissue connected, but creating a flap.

Season the chicken breast with the spice rub, including in the flap. Set aside.

Heat a large skillet over medium/high heat and add 1 tablespoon of olive oil. When the olive oil is hot, add onion and saute the onion for 4-5 minutes over medium heat. Add the spinach to the onion and toss. Cover the pan and let the spinach cook down for 1-2 minutes, stirring to ensure all the spinach cooks down. Transfer the spinach mixture to a large bowl and allow the spinach to cool for 10 minutes.

Add the cream cheese to the bowl once the spinach is cool and stir until the cream cheese and spinach are combined. Divide the spinach mixture into fourths.

Stuff each chicken breast with 1/4 of the spinach mixture by placing it in between the flap. Secure the spinach cream cheese filling by closing the flap and securing both edges of the chicken breast with 2-3 toothpicks or more until it holds together. Repeat with each chicken breast.

Heat a large oven-safe skillet over medium/high heat. Add olive oil. When the olive oil is fragrant, add the stuffed chicken breast to the pan. Sear for 2-3 minutes on each side to brown.

Carefully place the skillet into the oven (be careful, the handle might be hot) and bake at 375ºF for 20-30 minutes, flipping halfway.

Use a meat thermometer to check the internal temperature of the chicken breast. Make sure it’s at least 165ºF before removing it from the oven. Let rest for at least 10 minutes before eating.

If there is any melted cheese in the bottom of the skillet, be sure to pour the melted cream cheese over the chicken breasts before serving.