How long to bake matzah, butter and sugar at a lower temperature
I found some recipes that bake the matzah at 350º or 375º:

https://www.onceuponachef.com/recipes/chocolate-toffee-matzo-crack.html
https://www.thekitchn.com/recipe-chocolate-caramel-matzo-brittle-recipes-from-the-kitchn-47589
https://www.chowhound.com/recipes/matzo-brittle-28236
https://www.saveur.com/article/Recipes/Dark-Chocolate-Matzo-Brittle

They call for a baking time between 5 and 15 minutes. All those recipes are fairly similar and maybe similar enough to yours that they'll work for you.