In a large bowl, mix to combine the ground chicken, salt, pepper, garlic powder, parsley, panko, egg yolk, lemon zest. Once well combined, form into 1 ½-inch meatballs. Damp hands will make this easier as the chicken can be sticky.
In a large deep non-stick skillet, heat the oil over medium heat. Once hot, add the meatballs in a single layer, working in batches as needed. Brown the meatballs on all sides, about 3 minutes per side. The meatballs do not need to be cooked through as they will finish cooking in the sauce. Once browned, set aside on a plate and continue until all the meatballs are browned.
Make the Sauce:
In the same skillet, reduce heat to medium-low and melt the butter. Add the garlic, red pepper flakes, cassava flour. Stir, toasting the flour, for 1 minute.
While whisking, pour wine into skillet to combine. Continue whisking and add the chicken broth until well combined. Add the capers, parsley, lemon juice, salt, and pepper. Stir to combine then increase heat to a rapid simmer.
Reduce heat to a light simmer then nestle the meatballs back into the sauce. Cover and cook until the meatballs are cooked through, 5 to 7 minutes.