Preheat the oven to 400 degrees.
To make the crust, line a baking sheet with a piece of parchment paper. Lay down one sheet of fillo dough on top of it. Keep the rest of the fillo sheets covered with a clean, wet kitchen towel to avoid drying out. Quickly brush the sheet with a thin layer of olive oil using a pastry brush. Layer another sheet on top of it, and brush that one with a thin layer of olive oil. Continue this step until all of the sheets are layers and brushed with oil.
Gently fold the edges of the dough over to form the crust’s rim. Brush with a small amount of olive oil to help keep it in place.
Carefully spread the cashew ricotta over the crust. You may need to use your hands to avoid tearing the fillo dough.
Layer the tomato slices to top of the ricotta.
Gently toss the asparagus with the remaining teaspoon of olive oil. Layer them on top of the tomatoes. Press down lightly to ensure the veggies are firmly in place in the ricotta. Sprinkle with salt and pepper.
Bake for 20 – 25 minutes, or until the crust is golden brown.
Sprinkle the cooked tart with lemon zest and chopped fresh basil leaves.
Using the parchment paper, carefully slide the tart from the baking sheet to a cutting board to slice it. Serve hot.