Bring a large pot of salted water to a boil and cook the whole wheat linguine according to package directions until al dente.
While the pasta cooks, season the chicken breast on both sides with the sea salt and black pepper.
Heat the olive oil in a large skillet over medium-high heat and sear the chicken breast until golden brown and cooked through, approximately 5-6 minutes per side.
Remove the chicken from the skillet and let it rest for 3 minutes before slicing it into thin strips.
In the same skillet, add the minced garlic and sun-dried tomatoes, sautéing for about 1 minute until the garlic is fragrant.
Drain the pasta, reserving a small amount of pasta water, and add the linguine to the skillet along with the baby spinach, sliced chicken, and basil pesto.
Toss the mixture over low heat until the spinach is just wilted and the pasta is thoroughly coated, adding a splash of pasta water if needed to loosen the sauce.
Finish the dish with a squeeze of fresh lemon juice and serve immediately.