1Preheat oven to 425. Whisk oil with herbs, mustard, lemon zest, lemon juice, salt and pepper until well combined. Toss potatoes with 2 Tablespoons of oil mixture. Spread out on rimmed baking sheet lined with parchment paper. Roast for 20 mins.
2Brush 2 Tablespoons of oil mixture over salmon. Push potatoes to edges of baking sheet. Center salmon in middle. Roast for 10 mins.
3Toss asparagus with remaining oil mixture arrange along side of potatoes. Roast for an additional 10 mins or until potatoes are fork tender and fish flakes easily with a fork
4Caper aioli: Whisk egg yolks with lemon juice, water and garlic in a small non reactive bowl. Set bowl over a saucepan of simmering water(do not let the bottom of the bowl touch the water)Cook whisking constantly for 1-2 mins or till thickened. Remove bowl from heat cool 10 mins.
5Gradually drizzle oil into yolk mixture whisking vigorously until smooth and thick. Stir in capers.
Plate salmon, potatoes and asparagus and serve the sauce on the side.