To a high-speed blender, add 4 sliced ripe bananas, lemon juice, sweetened condensed milk, turmeric and xanthan gum, then blend for 1-2 minutes (or until it achieves a lump-free, pudding-like consistency).
Transfer the pudding to a bowl and allow it to continue thickening for 10-15 minuetes, or until it reaches a custard-like consistency.
While pudding is thickening to a custard, proceed to slice the other 4 ripe bananas into round but firm slices (approx. 1/4" in thickness) and begin layering your pyrex dish, first with cookies then with the sliced bananas.
Once pudding achieves a custard-like consistency, add thawed whipped topping to the bowl and gently fold together with custard until blended.
For the next layer, add half of the blended custard base and spread it around until it forms an even layer and the whole bananas are completely covered.
Repeat layers until all of the cookies, whole bananas, custard and whipped topping have been used up.
Cover bowl and chill in refrigerator for a minimum of 4 hours before serving (optional).