Add 1/3 of the salmon to the bowl of a food processor. Pulse until the salmon is smooth, about 10 to 15 seconds.: The moment you start pulsing you will notice the texture shifting from flakey to silky, and the processor will emit a slightly sweet, oceanic aroma. This paste is essential because it acts like a glue, creating a tacky base that helps the patties stick together while still allowing the chopped fish to remain visible. If your processor warms up, pause occasionally to keep the fish cold, because heat can make the fats smear and turn the mixture mushy. A common mistake is over pulsing, which creates a completely smooth paste and robs the burger of pleasant texture. Aim for that smooth center and then stop.
Add the remaining salmon, parsley, garlic, onion powder (if using), Dijon, mayonnaise, lemon juice, salt, and pepper into the food processor with the smooth salmon. Pulse 6 or 7 times, until everything is combined and there are still chunks of salmon visible.: As you pulse, listen for the intermittent whir that tells you ingredients are blending without becoming uniform. You should smell garlic and lemon brightening up, and see flecks of parsley dispersed through the mixture. The goal here is to combine flavors while preserving texture, which is why short pulses are crucial. Avoid prolonged processing, which will overwork the fish and yield a dense patty. If the mix looks too wet, a light hand with bread crumbs later will correct moisture.
Transfer to a bowl and gently fold in the roasted peppers and bread crumbs.: Folding in the roasted red peppers and Panko bread crumbs by hand lets you control distribution and keep the peppers intact. You should feel slightly resistant as the crumbs absorb moisture, and the peppers should remain distinct pockets of color. Smell the sweet roasted pepper aroma and taste a tiny pinch to check seasoning. A common misstep is stirring vigorously, which can crush the peppers and overwork the mixture. Be gentle, use the padded part of your hand or a spatula, and stop once ingredients are evenly distributed.
Divide the mixture into 4 mounds, and then form each into a patty, about 3 to 4 inches in diameter. A hamburger press or large cookie cutter is helpful here, but not totally necessary.: When you form the patties, you should feel them hold their shape but still be cool to the touch. Press too hard and you will compress out air and moisture, creating a dense texture. The surface should be slightly tacky, and the edges neat. If the patties slump, they need more chilling or a touch more breadcrumbs. A common mistake is making patties too thin which causes them to overcook and dry out, so aim for roughly three quarters of an inch to one inch thick for juicy results.
Chill the patties for at least 20 minutes, or up to 24 hours.: Chilling firms the fats and proteins, making the patties far more resilient on the grill. You will notice the scent calm and the texture tighten as the patties chill. If you skip chilling, they are more likely to fall apart when you flip them, and you may lose those desirable internal pockets of flake. If preparing ahead, place patties on parchment and cover tightly, and know that up to 24 hours in the fridge is safe and often beneficial for flavor melding.
If grilling, turn your grill to medium-high heat. Lightly spray a grill pan, (or non-stick skillet) with cooking spray. Use a spatula to transfer the patties onto the grill pan and place over direct heat on the grill. Cook for 7 minutes and then carefully flip and cook for another 7 minutes. If cooking on the skillet, follow the same timing. The internal temperature of the burgers should be 135°F to 145°F.: As the patties hit the hot surface you will hear a gentle sizzle and smell the butter and fish browning. Look for golden edges and slight crust development before flipping. The second side should produce the same satisfying sizzle and deepen in color. Use an instant read thermometer to check that the center reaches between 135°F and 145°F , this ensures the fish is safe but still moist. Avoid repeatedly pressing the patties, which squeezes out juices and dries them. A common error is using too high heat which chars the exterior before the center cooks, so medium high provides the best balance.
Meanwhile, butter the buns and toast during the final cooking of the salmon burgers.: As the burgers finish, melt the unsalted butter in a skillet and toast the brioche buns until they are golden and fragrant. The buttered toast creates a slightly crispy barrier that prevents sogginess from sauces, and the warm bun complements the hot patty. You should hear a light hiss and see tiny bubbles in the butter as it toasts. Take care not to burn the bread, which happens quickly once the surface browns, so watch closely and transfer to a plate immediately when golden.
Serve at once on toasted buns, with lettuce, tomato, onion, and aioli, if desired.: The final experience is all about contrast, so assemble warm patties on the toasted brioche buns with crisp green leaf lettuce , juicy tomato slices, sharp red onion , and a smear of Rosemary and Garlic Aioli . The first bite should present the warmth of the patty, coolness of the lettuce, and a bright tang from the aioli. If your burger feels soggy, you likely used too much sauce or did not toast the buns well. Serve immediately to enjoy the textural interplay at its peak.