Preheat an oven, then stack tortillas and wrap in aluminum foil. Place directly on the oven rack and warm. Alternatively, you can char the tortillas over a stove top flame or wrap them in a damp paper towel and heat in a microwave in 30-second increments until warm. Place two warmed tortillas on each plate.
Combine eggs, heavy cream, chives, Kosher salt, and black pepper in a mixing bowl, then whisk to combine.
Heat a large nonstick skillet over medium-high heat, then add butter or neutral oil. Add the diced red onion and cook until softened, stirring occasionally. Lower the heat to medium.
Heat a large nonstick skillet over medium-high heat, then add butter or neutral oil. Add the diced red onion and cook until softened, stirring occasionally. Lower the heat to medium.
When the eggs are just slightly runny, add cubed cream cheese and ½ cup smoked salmon. Continue cooking until eggs are no longer runny, stirring often, then immediately remove from heat.
Divide scrambled eggs evenly between warm flour tortillas, then top with additional chives and diced red onion, if wanted. Serve immediately with lime wedges.