Form the dough into a flat disc and wrap in parchment paper. Place in the fridge for at least a half hour.
Remove the dough from the refrigerator and sprinkle the cutting board with oat flour and place the dough over the flour, then sprinkle more flour on top of the dough.
Roll out the dough to about a 1/4 inch thick. You may need to add more flour as you go.
Transfer to an 8 x 11 rectangle tart pan. Press into the edges and up the sides of the tart pan.
Add the wine and cook until it reduces to a syrup.
Add the mascarpone and stir until melted. Add the 2 cups of Manchego and salt then stir until incorporated then set aside. The Manchego doesn't need to be melted.
Evenly spread out the fennel, sprinkle on the diced red peppers and arrange tomatoes in a single layer. Spread the mascarpone mix over the tomatoes and then carefully create the lattice with the strips of bell peppers.
You can roast the peppers and the fennel the day before as well as grate the cheese.