Preheat your oven to 200°F and line two baking sheets with paper towel.
Using the 3mm-blade, spiralize your zucchinis. Divide the zucchini noodles between the two paper towel-lined baking sheets in a flat layer. Sprinkle evenly with salt.
Bake the zucchini noodles in the oven for 40 minutes to dry them out. (Don't worry the paper towel won't burn at such a low temp!) Once cooked, cover with paper towel and press out any excess moisture. Repeat once more with an additional paper towel. Set aside.
Lightly spray your casserole baking dish with cooking spray. Bring your oven up to 375°F and place the Greek yogurt, barbecue sauce, and 1 cup of cheese in a large saucepan over medium-low heat. Cook until the cheese just begins to break down and look melted and “stringy,” about 8-10 minutes, whisking regularly.
While the cheese melts, toss together the shredded chicken breast, cilantro, and dried zucchini noodles in a large bowl. Lightly break up the mixture with a fork and knife to make it easier to evenly mix, as well as cut, once cooked.
Once the cheese has started to melt, pour the sauce over the zucchini noodle mixture, and season with a pinch of pepper. Mix well until the sauce evenly coats the noodles.
Spread the casserole into a dish and bake for 20 minutes. Sprinkle with the remaining cheese, and bake until golden brown and bubbling, about 20-25 more minutes.
Once cooked, let the casserole cool for 20 minutes (don’t skip this!) to let it set and absorb some of the water.
Cut, drizzle with extra barbecue sauce, and garnish with cilantro, if desired.