I wouldn’t. When testing my vegan lemon poppyseed muffins, I tried to use a lot of lemon juice and my cake kept sinking. If you want more lemon, try adding a teaspoon of lemon extract to the batter. Or make a glaze from vegan powdered sugar, lemon juice, and a splash of non-dairy milk to add to the cake later. That’s what I did for my vegan lemon loaf and it’s fantastically lemon flavored.