Preheat the oven to 350°F and line a baking sheet with parchment paper; optionally place a wire rack on the sheet.
In a shallow dish whisk together the milk and eggs until combined.
Place the corn flakes, chopped parsley, smoked paprika, 1/2 teaspoon kosher salt, and black pepper in a food processor and pulse until the flakes are coarse breadcrumbs; transfer to a second shallow dish.
Working one at a time, dip each chicken tender into the milk-and-egg mixture, letting excess drip off, then press into the cornflake mixture to coat both sides; place on the prepared baking sheet.
Repeat with the remaining tenders, arrange them in a single layer, and lightly spray the tops with cooking spray.
Bake for 15 minutes, flipping once halfway through if not using a wire rack, until the coating is golden and the chicken reaches 165°F.
While the chicken bakes, stir together the mayonnaise, ketchup, minced onion, sweet relish, and a pinch of kosher salt to make the special sauce.
Serve the baked chicken tenders warm with the special sauce and an optional sprinkle of extra parsley.