Preparation

1. To make the sauce, line a colander with a coffee filter, place over a bowl and strain the yogurt 30 minutes.
2. Line a second colander with a coffee filter.
3. Combine cucumbers and salt and strain for 30 minutes to remove moisture.
4. Rinse cucumbers to remove much of salt and squeeze dry.
5. Combine strained yogurt, cucumber, garlic, mint, flax oil and lemon juice in a small bowl and chill 30 minutes while you prepare the salmon burgers.
6. Cut salmon into 1-inch cubes.
7. Place salmon, mustard and green onions in a food processor and pulse 4-6 times until salmon is minced to the consistency of ground beef.
8. Put salmon in a bowl, add feta, breadcrumbs, oregano and egg white, and mix until well combined.
9. Form the salmon mixture into 4 burgers.
10. Brush each with olive oil on both sides and sprinkle with salt and pepper.
11. Preheat and oil the grill according to the manufacturer's instructions.
12. Cook burgers 3-4 minutes on each side. Serve with tzatziki sauce.