Sprinkle yeast and sugar into a bowl with 1/4 cup warm water. Stir to dissolve and let stand until foamy, about 10 minutes.
Combine buttermilk, molasses, honey, and 4 Tbsp. butter in a small bowl.
In a large bowl, combine salt, sesame and sunflower seeds, and whole wheat flour. Add yeast and buttermilk mixtures and stir until smooth. Add drained cracked wheat and stir to combine.
Using a wooden spoon to mix, add all-purpose flour, 1/2 cup at a time. Stir until soft dough forms (you may need to use your hands to blend it well). Turn dough out onto a floured surface and knead until dough is soft and springy, about 7 or 8 minutes. Add more flour, 1 Tbsp. at a time, if needed. The dough will be a bit sticky.
Place dough in a greased bowl; turn it in the bowl to grease the top. Cover with plastic wrap and let dough rise in a warm spot until doubled in size, about 1 hour and 15 minutes.
Prepare 2 baking sheets by lightly greasing and topping with a thin layer of cornmeal. Set aside.
Preheat oven to 350°. Gently deflate dough; turn out onto lightly floured surface; divide into 3 equal portions and shape into 3 round or oval loaves. Place on prepared pans. Melt and cool remaining Tbsp. butter and spread over tops of loaves. Sprinkle with a few sunflower seeds. Cover loosely with plastic wrap and let rise 30 minutes.
Bake in preheated oven for 35 to 45 minutes until brown. Cool on racks and eat warm.