Before You Begin

This recipe requires an 8-inch square metal baking pan. Avoid using a ceramic or glass dish, which will increase the cooking time and could cause the eggs to overcook during cooling. We like the flavor and texture of rye bread for these sandwiches, but you can substitute 4-inch bulkie rolls, kaiser rolls, English muffins, or burger buns, if desired. If you omit the salmon from your sandwiches, you may want to season the eggs with additional salt after baking. For maximum efficiency, gather and prepare the sandwich fillings while the eggs cook, and toast the bread while the eggs cool. Alternatively, let the eggs cool completely after cutting them, stack them in an airtight container, and refrigerate them for up to three days. To reheat, arrange the egg squares on a large plate and microwave at 50 percent power until they're warm, 2 to 3 minutes.

1. Adjust oven rack to middle position and heat oven to 300 degrees. Whisk eggs and salt in large bowl until well combined. Whisk in ⅔ cup water. Spray 8-inch square baking pan with vegetable oil spray. Pour egg mixture into prepared pan and set pan on rimmed baking sheet. Add 1½ cups water to sheet. Transfer sheet to oven and bake until eggs are fully set, 35 to 40 minutes, rotating pan halfway through baking. While eggs bake, place onion in bowl, cover with ice water, and let sit for 15 minutes. Drain onion well and pat dry. Remove pan from sheet, transfer to wire rack, and let cool for 10 minutes.
2. Run knife around edges of pan and, using dish towel or oven mitts, invert eggs onto cutting board (if eggs stick to pan, tap bottom of pan firmly to dislodge). Cut into 4 equal squares. Spread yogurt on 4 slices of toast. Sprinkle dill over yogurt. Using spatula, transfer 1 egg square to each sandwich. Top each egg square with smoked salmon and then onion. Set remaining 4 slices of toast over onion and serve.

If you’d like to plan for a meal on the go, prepare the eggs in advance, cut them into squares, and let them cool completely. Stack the squares in an airtight container and refrigerate them for up to three days.

To reheat, arrange the egg square(s) on a plate and microwave at 50 percent power until they’re warm (about 45 seconds for a single square or 2 to 3 minutes for four squares).