Combine the warm water, sugar and yeast in the bowl of a stand mixer Allow the mixture to sit for 5 minutes or until the mixture begins to foam.
Add the flour and salt and using the dough hook attachment, mix on low speed until well combined. Change to medium speed and knead until the dough is smooth and pulls away from the side of the bowl, approximately 4 to 5 minutes.
Transfer the dough to a lightly greased bowl, cover with plastic wrap and let it sit for 30 minutes.
While the dough rests, combine the boiling water and baking soda in a container (I use a 10-inch square Pyrex glass container). Stir until the baking soda is dissolved. Set aside so the water starts cooling a bit.
Preheat oven to 450 degrees F and line a baking sheet with parchment paper.
In the meantime, turn the dough out onto a slightly oiled work surface and divide into 8 equal pieces. Roll out each piece of dough into a long rope - about 28 to 30 inch rope. Make a U-shape with the rope, holding the ends of the rope, cross them over each other and press onto the bottom of the U in order to form the shape of a pretzel.
Working with a couple of pretzels at a time, place the pretzels into the baking soda bath spooning the water over their tops; leave them in the water for about 1 minute before transferring them to the prepared baking sheet.
Sprinkle the pretzels lightly with coarse kosher salt or pretzel salt. Allow the pretzels to rest for 8 minutes, then place in the oven and bake for 10 minutes or until golden brown. Remove the pretzels from the oven and immediately brush with the melted butter.