Combine 1-1/2 cups flour, sugar, minced onions, undissolved yeast, salt and garlic salt in a large bowl. Heat milk, water and butter until very warm (120° to 130°F). Gradually add to flour mixture. Beat 2 minutes at medium speed of electric mixer, scraping bowl occasionally. Add egg and 1 cup flour; beat 2 minutes at high speed. Stir in enough remaining flour to make a soft dough. Knead on lightly floured surface until smooth and elastic, about 8 to 10 minutes. Cover; let rest 10 minutes.
Divide dough into 3 equal pieces; roll each piece to 30-inch rope. Braid ropes, pinch ends to seal. Tie knot in center of braid; wrap ends around knot in opposite directions; tuck under to make a round loaf. Place on greased baking sheet. Cover; let rise in warm, draft-free place until doubled in size, about 45 minutes.
Onion Topping: Combine onion and olive oil in a skillet. Cook over medium heat, stirring constantly until onion is tender, about 3 to 5 minutes. Remove from heat; stir in dill and garlic salt.
Sprinkle loaf with Onion Topping and kosher salt. Bake at 375°F for 35 minutes or until done. Remove from sheet; cool on wire rack. Brush with melted butter while warm.