• To make the kreplach dough:
• Pour the flour into a large bowl. Use your fingers to make a small well. Crack the egg into the hole and lightly incorporate with your hands.
• Slowly add the water, kneading the dough until a light, moist ball emerges which has incorporated all of the flour. Try not to over-knead the dough.To make the salmon filling:
• While the kreplach dough is sitting, make the salmon filling. Heat the oil in a small frying pan and saute the onion until golden.
• Transfer the onion to a bowl and add remaining ingredients. Lightly mix in the rest of the ingredients. Refrigerate the filling for a half hour.To assemble and cook the kreplach:
• Divide fist-size pieces of dough and roll out well on a floured pastry cloth or floured wax paper. Using a knife, cut the dough into 2-inch-by-2-inch squares.
• Put a heaping teaspoon of filling in the center of each square. Fold the dough over the filling to form a triangle.
• Dip your fingers in water and moisten the edges to keep the seams closed. Use a fork to make decorative, light indentions.
• Drop in a pot of boiling water. Boil for 5 minutes or until they have a translucent look to them, indicating that they are done.
• Kreplach can be prepared stored in an airtight container or Ziploc bag, up to 2 days in advance, or frozen, see notes.Tomato Soup
• In a large pot, saute the onions, garlic, and salt in olive oil for 5 minutes. Add the rest of the ingredients except for the mayonnaise or sour cream and bring to a simmer.
• Cook until the flavors are blended and the soup is thickened, about 30 minutes. Before serving, stir in the mayonnaise or sour cream. Spoon into individual bowls and serve with salmon dill kreplach.

Tips

• Pan-fry leftover salmon filling to make delicious fish patties.
• To freeze kreplach, line a cookie sheet with aluminum foil and spray with nonstick cooking spray, or parchment paper. Place the kreplach on the tray and freeze until solid, about 1hour. Remove from freezer and transfer the kreplach to plastic bags. Store in the freezer for three months.
• To roast garlic, cut the top end off of a head of garlic. Lightly spray with non-stick cooking spray. Wrap in aluminum foil and roast in a 400℉  oven until very soft, golden and fragrant.