In a large bowl, stir together yeast and warm water. Set aside for 5 minutes.
Add cottage cheese, sugar, egg, onion, dillseed, salt, and baking soda. Beat with an electric mixer on low to medium speed until well mixed. Beat in as much of the flour as you can. Turn out onto a well-floured surface. Knead in enough of the remaining flour to make a moderately stiff dough that's smooth and elastic (6 to 8 minutes total).
Place dough in a large greased bowl; turn once to grease surface. Cover and let rise in a warm place until doubled (about 1 hour).
Punch the dough down. Turn out onto a lightly floured surface. Let rest for 10 minutes.
Form into one large round loaf or two smaller round loaves. Place on a greased baking sheet. Flatten large loaf into a 6-inch circle and small loaves into 4-1/2-inch circles. Cover; let rise until nearly doubled (about 30 minutes).
Bake in a 350 degree F oven about 30 minutes for the large loaf or 20 minutes for smaller loaves or until bread sounds hollow when tapped. Transfer to wire racks. Brush tops of loaves with butter. Sprinkle with coarse salt. Cool completely. Makes 1 large or 2 smaller loaves (12 servings).