Preheat the oven to 425 °F. Lightly spray a large foil-lined baking sheet with nonstick spray.
Stir all the Cajun spice blend ingredients together in a small bowl and set aside.
The potatoes take the longest time to cook, so we'll start with those. Slice the potatoes up into wedges and toss them with 1 teaspoon olive oil + 1 tablespoon of the Cajun spice blend in a large bowl.
Spread the potato wedges in an even layer on the prepared baking sheet. Roast them for 15 minutes at425 °F , give them a stir, and put them back in for another 10 to 15 minutes (cooking time depends on how large and thick your potato wedges are.)
Meanwhile, while the potatoes are in the oven, heat a skillet over medium-high heat and spray it lightly with nonstick spray.
Rinse your fish fillets, pat them dry and give them a light spray with nonstick (or an olive oil mister also works)
Rub the remaining 1 tablespoon of the Cajun spice blend onto both sides of the fish.
Cook the fish in a hot skillet, about 5 minutes per side.
Whisk together all the zesty sauce ingredients in a small bowl, and use it as a dipping sauce for the fish and potatoes.