For the salmon: In a bowl, whisk together the salt, sugar, lemon and lime extracts.
Lay an 18-inch-long piece of plastic wrap on a work surface. Mound half of the seasoning mixture in the center of the plastic wrap and press it into a rectangle slightly bigger than the piece of salmon. Place the salmon on top of the mixture and cover with the remaining mixture. Wrap tightly in the plastic and refrigerate 8 hours or overnight.
Remove the salmon from the cure and quickly rinse under cold water. Pat dry and refrigerate until ready to serve.
For the spice-poached eggs: In a shallow dish, combine the vinegar, paprika and garlic powder and whisk until dissolved. Carefully crack the eggs into the dish with the vinegar and let stand 5 minutes.
Meanwhile, fill a wide pot approximately 3 inches deep with water. Bring the water to a simmer and season to taste with salt. Adjust the heat so the water maintains a simmer.
Carefully lift the eggs from the vinegar mixture with a slotted spoon and place into the simmering water. Cook the eggs until just firm, 3 to 4 minutes. Lift eggs out with a slotted spoon and gently blot with clean paper towels to remove excess moisture. Serve immediately or transfer to ice water to hold (see Cook's Note).
For the arugula salsa verde: Combine the arugula, oil, capers, oregano, vinegar, garlic and thyme in a food processor and pulse to chop well, but do not puree it. Season to taste with salt and pepper.
For the toast: Drizzle 1 tablespoon olive oil over both sides of the bread slices. Toast or grill the bread until lightly browned on both sides, but still tender and soft in the center. Set the toast on a rack to cool.
Meanwhile, cut the avocados in half and carefully remove the pits. Scoop the flesh from the skin and place in a mixing bowl. Add the lime juice, garlic powder, salt and remaining tablespoon olive oil. Mash the avocado with a fork until well mixed, but not smooth. Fold in the herbs.
For the everything spice mix: Stir together the poppy seeds, sesame seeds, onion, garlic and salt in a small bowl and set aside.
For serving: Stir together the olive oil and the lemon and lime extracts in a small bowl and mix thoroughly. Cut the salmon into slices approximately 1/4-inch thick. Lightly brush the slices with the oil and pound lightly with the side of the knife to thin them out.
Divide the avocado mixture equally among the slices of toast and spread into an even layer. Sprinkle each with the everything spice mixture. Top half of the toast with the some of the sliced salmon and the other half with the spice-poached eggs and arugula salsa verde. Cut each slice in half and serve. Reserve any leftover salmon for another use; it will keep wrapped in the refrigerator for up to 1 week.
Poached eggs may be held in cold water until ready to serve: transfer cooked eggs to ice water until cool. Reheat chilled eggs in simmering water for 10 seconds before serving.