Measure flour and salt into large bowl. Cut butter into dry ingredients until you have a fine crumble.
Crack egg into another bowl; add vinegar and then a cup of water. Use fork to whisk egg mixture together. Pour egg mixture into dry ingredients almost all at once.
Mix together, gently gathering the dough.
Once the dough comes together, set it out onto a floured surface. Make sure the dough is combined and you are ready to roll.