Thaw coho salmon. Add to a bowl and mix with breadcrumbs, egg, onion powder, garlic powder, salt, and pepper. Gently mix until well combined. Form into 8, 2 ounce balls.
In another bowl, follow the same process with the ground beef, garlic powder, onion powder, salt, and pepper. Form into 8, 2 ounce balls.
Heat your griddle or grill to medium-high heat.
Place a ball of salmon mixture on the hot griddle. Place a piece of parchment paper on top. Use a sturdy spatula (or a burger press, if you have one) to firmly smash the ball into a thin patty, about 1/4 inch thick.
Cook the patties for 1-2 minutes until the edges are crispy and browned. Flip the patties and immediately place a slice of cheese on top. Cook for another 1-2 minutes until the cheese is melted and the patty is cooked to your desired doneness.
Repeat these steps for the salmon and beef patties.
Toast the burger buns on the griddle for a few seconds. Place the cooked patties on the bottom bun, add your desired toppings, and then top with the other half of the bun.
Serve the smash burgers hot with your favorite sides, like fries or a salad.
Enjoy!