In a large mixing bowl, combine warm water, yeast, and sugar. Let sit for 5 minutes until foamy.
Add flour, salt, and melted butter to the yeast mixture. Mix until a dough forms.
Knead the dough on a floured surface for about 5 minutes until smooth and elastic.
Place the dough in a greased bowl, cover, and let rise for 1 hour or until doubled in size.
Preheat the oven to 450°F (230°C). Line a baking sheet with parchment paper.
In a large pot, bring water and baking soda to a boil.
Divide the dough into 8 equal pieces. Roll each piece into a rope and tie into a knot.
Boil each knot in the baking soda bath for 30 seconds. Remove with a slotted spoon and place on the prepared baking sheet.
Sprinkle each knot with coarse sea salt.
Bake for 12-15 minutes or until golden brown.