I don't have a recipe, but you could use a typical recipe and adapt the flavorings.
Sweet Potato Pie Recipe | Leite's Culinaria

The idea comes from a dessert at a place I worked that included a vanilla bean sweet potato purée as one of the components.
I would steam or bake whole unpeeled sweet potatoes then scoop out and purée with some vanilla bean, salt, and maple syrup to taste then add some cream and eggs to make the custard. You need a good blender to get it silky smooth since you want to blend just the potatoes without the other ingredients so as not to incorporate air into the custard.
Pour into a baked tart shell (made similarly as the one linked to in that recipe, actually, though with part of the flour switched out for oat flour and less crust overall since you don't need as much for a tart as a pie) and bake until just set.
And no flour in the filling, because flour in baked custards is just uncalled for 99% of the time.