Bring a pot of salted water to a boil and cook the whole wheat spaghetti until al dente, then drain and set aside.
Season the chicken breast evenly with sea salt, black pepper, and dried oregano.
Heat the olive oil in a large skillet over medium-high heat and sear the chicken for 5-6 minutes per side until fully cooked.
Remove the chicken from the pan, let it rest for 3 minutes, and then slice into thin strips.
In the same skillet, add the minced garlic and sauté for 1 minute until fragrant.
Pour in the tomato puree and simmer over medium-low heat for 3-4 minutes to allow the flavors to meld.
Whisk in the plain Greek yogurt and add the fresh spinach, stirring until the spinach is wilted and the sauce is creamy.
Toss the cooked spaghetti and sliced chicken into the skillet, ensuring everything is well-coated in the sauce.
Garnish with freshly chopped basil and serve warm.