Bring a pot of salted water to a boil and cook the whole wheat penne according to package directions until al dente.
While pasta cooks, dice the chicken breast into bite-sized pieces and season with sea salt and black pepper.
Heat the olive oil in a large skillet over medium-high heat and sauté the chicken until golden and cooked through.
Mince the garlic and add it to the skillet, cooking for 1 minute until fragrant.
In a small bowl, whisk together the Greek yogurt, lemon juice, and lemon zest until smooth.
Drain the pasta, reserving 2 tablespoons of the cooking water.
Lower the skillet heat to low, then add the cooked pasta, reserved water, baby spinach, and the yogurt mixture.
Toss everything together gently until the spinach is wilted and the sauce is creamy.
Remove from heat immediately to prevent the yogurt from curdling, and garnish with parmesan cheese before serving.