Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Add potatoes to pan; lightly spray top of potatoes with cooking spray. Cook 8 minutes, turning frequently (don't let potatoes brown or crisp too much). Reduce heat to medium, and cook 20 minutes or until tender, stirring and turning frequently. Transfer potatoes to a bowl. Wipe pan with a paper towel.
Combine egg substitute, onion, dill, salt, pepper, and eggs in a large bowl. Stir in salmon. Add potato, and stir gently to combine.
Heat oil in pan over medium-high heat. Add potato mixture; cook 1 minute, gently pressing down potatoes with spatula to slightly flatten mixture in pan. Reduce heat to medium-low; cook 15 minutes or until egg has completely set around edges and has just set in the center of pan, gently shaking pan frequently. (Tortilla should easily move around the pan.) Place a plate upside down on top of tortilla; invert onto plate. Carefully slide tortilla, cooked side up, into pan. Cook 5 minutes or until knife inserted in center comes out clean, gently shaking pan occasionally. Carefully loosen tortilla with a spatula; transfer to serving platter. Let cool at least 10 minutes. Cut into 8 wedges, and top with sour cream. Garnish with dill, if desired.