Line an 8-inch square baking pan with parchment paper and preheat the oven to 375°F (190°C).
To make the base, combine the flour, sugar, baking powder, and salt in a large bowl. Add the oil and water and stir until a crumbly dough forms.
Press the mixture firmly into the prepared pan and bake until lightly golden around the edges and just firm.
In a blender, blend the sweet potato puree, coconut milk, and sugar until smooth. Add the cornstarch, vanilla, salt, cinnamon, nutmeg, and cloves and blend again until completely smooth.
Pour the filling over the warm crust and smooth the top. Lightly dust with cinnamon.
Reduce the oven temperature to 325°F (160°C) and bake until the edges are set, the center is no longer moving when gently shaken, and the surface looks matte rather than glossy.
Cool completely in the pan before lifting out and slicing into bars.