PREHEAT the oven to 350°F
LINE a tart pan with a removable base and set aside
PREPARE the crust: in a large bowl, whisk together the egg white, melted butter (or oil), water and stevia. Add the bread mix, and mix until combined
GATHER the dough into a ball and transfer to the prepared tart pan. Use the heel of your hand to gently press the dough into an even layer across the bottom of the pan, then up the sides. Use your fingertips to pinch off the excess dough that rises above the edge of the pan
TOP the crust with a layer of parchment paper, then fill the shell with pie weights (see note) and cook for 10 minutes
MAKE the filling: in a stand mixer fitted with the beater attachment, or using a hand mixer, thoroughly mix the eggs and yolks together so that no clumps of white or yolk remain. Add the lemon zest, juice, and stevia, and beat until combined
REMOVE the parchment paper and pie weights (or beans) and pour the filling into the crust and bake, still at 350F, for 35-45 minutes until a firm crust forms on top, but the filling is still a little soft to the touch. If you prefer a less custard-y texture, bake an extra 5 minutes until firm
REMOVE and cool before serving. Garnish with lemon slices if desired, but if using raw lemon slices, remove them before eating. Alternately, you can dust the top of the tart with powdered cane or coconut sugar before slicing