• Oil the bottom and sides of a 9 inch (23 centimeter) spring form pan with pan spray, making sure to get the bottom corners well. I use a nonstick pan - if using a different type of pan, spray the bottom and sides of the pan and line the bottom with a piece of parchment paper, spray the bottom again.
• Preheat oven to 350 Fahrenheit (177 Celsius). Set baking rack to the middle position.

For the Pastry:

• In a large mixing bowl whisk together flour, corn starch, sugar, baking powder, and sea salt. Using a pastry cutter, cut in the butter until the mixture resembles a fine meal. A few larger pea size chunks are okay. Make a well, then add the egg, lemon zest and vanilla extract. Use your hands to mix the dough, just until it begins to come together. The dough will be somewhat crumbly at this point, but should hold together after squeezing it in your fist.

  Press the mixture into the bottom and up to one inch high on the sides of the spring form pan, as evenly as possible. Use the back of a measuring cup to help firmly press and work the dough into the pan. If at any time the dough becomes too sticky to work with, place it in the refrigerator for about 10 minutes, then continue to press the dough into the pan. Refrigerate for 10 minutes.

  After removing the pastry from the refrigerator, use your index finger to gently press the top edge of the pastry so that it is somewhat even all the way around the edge.

For the Filling:

• In a large mixing bowl, whisk together the sugar, flour, and corn starch. Add the blueberries, peaches and lemon juice. Toss to coat. Pour the fruit mixture and all its juices into the pastry lined spring form pan.

  Update: Wrap the bottom of your pan in foil just in case there's a butter leak.

To Bake:

• Bake at 350 Fahrenheit for 1 hour and 10-20 minutes OR until the pastry is golden, fruit is starting to bubble and center is set.

To Serve:

• Set on a cooling rack and allow the tart to cool completely before removing the spring form, about 1 1/2-2 hours. Removing prior to complete cooling may break the crust. Run a sharp knife around the edge of the pastry crust and carefully remove the ring. Set on serving platter and serve at room temperature.
• Share with fresh vanilla bean whipped cream or vanilla ice cream.
• Although this tart is best the day it's made, it can be stored in a covered container in refrigerator for up to three days. Gently reheat in a 350 F oven for about 10 minutes if desired.