Preheat oven to 400°F. Line a baking sheet with foil. Place the 1 lb salmon filet on the baking sheet, season with Kosher salt and black pepper, and brush with 1 tbsp olive oil. Bake 15–20 minutes until cooked through and opaque. Remove from oven and let cool until you can handle it, then flake with a fork and remove any bones or skin.
While the salmon cools, heat a skillet over medium heat and add 1 tbsp olive oil and 1 tbsp unsalted butter. Add the finely diced medium onion and diced red bell pepper and sauté until softened and golden, about 8–10 minutes. Remove from heat and let cool slightly.
In a large bowl combine the flaked salmon, sautéed onion and bell pepper, 1 cup Panko breadcrumbs, the slightly beaten 2 large eggs, 4 tbsp mayo, 1 tsp Worcestershire sauce, 1 tsp sriracha, and 1.5 tsp Old Bay seasoning. Season with additional Kosher salt and black pepper if desired. Gently mix until just combined.
Wipe out the skillet and heat it over medium-high. Add the remaining 2 tbsp olive oil and the remaining 1 tbsp unsalted butter.
Form the salmon mixture into patties (about 1½ tablespoons of mixture per patty) and gently flatten them.
Cook the patties in the hot skillet without overcrowding: 3–4 minutes per side, until golden brown, crispy, and heated through. Cook in batches as needed, adjusting heat so they don’t burn and adding oil/butter if the pan becomes dry.
Transfer cooked patties to a paper-towel-lined plate to drain briefly, then serve.