Pat the chicken breasts dry with a paper towel. Season generously on all sides with the Cajun seasoning.

Heat olive oil in a large skillet over medium-high heat. Place the seasoned chicken in the hot skillet and cook for 5-7 minutes per side, until golden brown and cooked through (internal temperature reaches 165°F). Remove the chicken from the skillet and set aside on a plate.

In the same skillet, reduce the heat to medium. Add the diced onion and cook, stirring occasionally, until it begins to soften, about 3-4 minutes.

Add the minced garlic and cook for another 30-60 seconds until fragrant. Pour in the chicken broth, using a whisk or wooden spoon to scrape up any flavorful browned bits from the bottom of the pan.

Reduce the heat to low. Add the cubed cream cheese and whisk constantly until it has completely melted into the sauce. Turn off the heat.

Slowly whisk in the plain Greek yogurt until the sauce is smooth and creamy. It's important to do this off the heat to prevent the yogurt from curdling.

Return the skillet to low heat. Stir in the fresh spinach until it wilts. Slice the cooked chicken and add it back to the skillet. Toss gently to coat the chicken in the sauce. Serve immediately.