Stir the yeast in the lukewarm water, adding a bit of the sugar to it. Let is sit for 10-15 minutes until frothy.
Place the remaining ingredients in the bowl of a stand mixer attached with a dough hook. Add the yeast mixture and knead for 5-6 minutes (or longer if kneading by hand) until a ball of dough forms, scraping the sides of the bowl as needed.
Remove the dough, lightly spray the bowl with oil, return the dough to the bowl, cover with plastic wrap and put in a warm or room temp place to rise for at least an hour or until doubled in size.
Punch the dough to deflate it then divide it into 8 equal pieces. Roll the pieces into balls and flatten them slightly (1/2-3/4 inch thick). Place them on a lined baking sheet. Let the rolls rise for another hour or until nearly doubled in size. Brush with some butter (or for a glossy finish use egg beaten with 2 teaspoons of water). Sprinkle with sesame seeds if using.
Have the oven preheated to 375 degrees F. Bake the buns for 15-18 minutes until golden. Remove and let them cool.