Pour sugar into a dish and dip each cut half of lemon into sugar to lightly coat.
Place lemons, sugar-side down onto a hot grill until charred, about 5 minutes (make sure you have the stove fan on if you do this inside).
Once cool, juice lemons and place liquid into a bowl. If desired, pour mixture through sieve to remove pulp and needs, then pour into a large pitcher.
Heat 1 cup of water with remaining sugar, stirring until dissolved. Pour into pitcher then top up with enough water until your desired sweetness is achieved.