Drain the raspberries in a strainer set over a bowl. Preheat the oven to 400 degrees . Using your fingers, combine the butter, 1/2 cup of the sugar and 1 1/2 cups of the flour and blend together until coarse crumbs form. Pour the mixture into an ungreased nonstick 9-inch springform or cake pan and press down evenly to form a crust. Bake the shortbread crust until lightly golden, about 20 minutes.
Remove the shortbread from the oven and reduce the temperature to 325 degrees . Scatter the drained raspberries evenly over the baked shortbread.
Beat the eggs with the remaining 3/4 cup of sugar until thick and pale yellow. Whisk in the lemon zest, the lemon juice and the remaining 1/4 cup of flour. Pour the lemon cream over the raspberries and bake the tart until the custard is set, about 30 minutes. Let cool, then dust with confectioners sugar.
Shortbread crust was a disaster! Please check ratio of flour to butter.