Cook tortellini according to package directions, drain, and return it to the pot.
Meanwhile, heat olive oil in a large skillet over medium-high heat until shimmering and swirl to coat the bottom of the pan. Chop the chicken into bite-sized pieces, season with sea salt & pepper, and brown 3-4 minutes per side over medium-high heat or until cooked through.
Remove chicken from the skillet and dump it into the pot with the tortellini. Reduce heat to medium under the same skillet you used for the chicken, add a little more olive oil, and saute the garlic very briefly. Add the grape tomatoes and season them with crushed red pepper and basil, then continue to saute tomatoes over medium heat for about eight minutes, stirring occasionally and scraping the browned bits off the bottom, until tomatoes are just beginning to wrinkle and burst.
Add the cooked tortellini and chicken into the skillet with the tomatoes. Reduce heat to medium-low and stir in pesto to coat, then gently stir in spinach. Continue stir gently and occasionally over medium-low heat until spinach is nicely wilted into the pasta, then serve.
Notes
I actually found half price chicken tenders on clearance this week, but it's fine to use regular boneless skinless chicken breast since you're chopping it into pieces anyway.