In a large bowl stir together self-rising flour and sugar

In a separate container (I just use the measuring cup) mix together milk, lemon juice, eggs and vanilla

Stir the milk mixture into the flour just until combined, don't over-mix. Stir in the melted butter

Cook in your waffle iron according to its instructions

Brush the waffle iron with oil or spray with non stick cooking spray as needed

For Belgian waffles, I would separate the eggs, add the yolks to the batter, beat the whites until fluffy, then gently mix them into the batter as well