Season the chicken breast evenly with sea salt, black pepper, and dried oregano.
Heat the olive oil in a medium skillet over medium-high heat until shimmering.
Add the chicken to the skillet and sear for 5-6 minutes per side, or until golden brown and cooked through to an internal temperature of 165°F.
Remove the chicken from the skillet and set aside on a plate, keeping it warm.
In the same skillet, add the diced onion and minced garlic, sautéing for 2-3 minutes until softened and fragrant.
Stir in the chopped sun-dried tomatoes, coconut milk, chicken broth, and nutritional yeast, scraping any browned bits from the bottom of the pan.
Bring the sauce to a gentle simmer for 3-4 minutes until it begins to slightly thicken.
Add the fresh baby spinach to the skillet and stir until it is just wilted and bright green.
Return the chicken to the skillet, spooning the creamy sauce over the top, and serve immediately.