In a large mixing bowl or into a food processor, combine flour, salt, lemon zest and sugar. Then add cold butter (cut into 1/2 inch cubes for easy combining). Mix until it resembles corn meal.

In a small bowl, combine the egg, vinegar, and water. Whisk together, then add gradually to the flour mixture in the food processor, mixing as you pour. Mix until dough form a ball. Carefully watch the consistency of the dough as you may need less liquid mixture or a touch more water depending upon the humidity in the region in which you live.

Roll into a ball and flatten into a round disc about 1-2 inches thick. Wrap in plastic wrap and place in the refrigerator for at least 30 minutes, and up to three days if necessary.

Remove from the refrigerator and roll out to size including a 1-inch edge for your tart dish (or dishes). Place in your tart pan(s) with removable bottoms. If there are cracks or it is an imperfect roll-out, don't worry. This dough is perfect for pressing into place, so do not be afraid to take loose pieces and place where necessary. Roll the rolling pin over the top of the edges to create the clean edge. Place in the freezer for 20-30 minutes until very firm. Heat the oven to 425 degrees Fahrenheit. Remove the tart dough from the freezer, prick with a fork. Then line with foil and place pie weights or beans on top to hold the shape of the dough. Bake for 12-15 minutes until crust is set and just beginning to brown. Remove the foil and bake until crust is golden brown, 10-12 minutes more approximately. Place crust on a wire rack and allow to cool completely.

In a medium sauce pan, mix the sugar, flour, and salt. Whisk in the milk until smooth.

On medium-high heat, bring to a gentle boil, whisking constantly. Boil for four to five minutes until the mixture thickens (it may take longer depending on the quality of your saucepan, but so long as you are whisking, it won't burn). Remove the pan from the heat. In a small bowl, whisk the egg yolks. Gradually whisk in about one cup of the hot-milk mixture. Pour the egg yolk mixture into the saucepan and, whisking constantly, simmer for two to three minutes until slightly thicker. Remove the pan from the heat.

Add the butter and vanilla and stir until the butter has melted completely. (If necessary, strain the custard through a fine sieve set over a medium bowl.) Place plastic wrap directly on the surface of the custard to keep a skin from forming. Refrigerate until cool, about one hour.

Cut the fruit into narrow slices, thickness to your preference (unless raspberries and then no slicing is involved). Spread the custard into the prepared, cooled crust. Top with fresh fruit. Serve immediately or refrigerate and remove when ready to serve.