Preheat oven to 400 F.
Place large skillet over medium-high heat and add 1 tablespoon olive oil. Season salmon portions with salt and pepper, to taste, and place skin sides down in pan. Cook 2-3 minutes until skin is crispy. Place on sheet pan, skin sides up, and bake 6-7 minutes. Remove from oven and let rest.
In same skillet, add remaining olive oil then add peppers and potatoes. Cook 6-7 minutes until peppers soften and potatoes start to caramelize.
Add paprika, cayenne and peas; stir and cook 2 minutes. Add tarragon.
To make romesco sauce: In clean pan, heat olive oil and gently fry garlic, nuts and bread until toasted.
In blender, process red pepper, tomato puree and vinegar until smooth. Add toasted nuts and bread; process to desired consistency.
To make aioli: In bowl, whisk mayonnaise, garlic, olive oil, lemon zest and juice, salt and pepper.
Place several spoonfuls of aioli on plate. Top with potatoes, peppers and salmon, skin side up. Top with romesco sauce.