Add ground beef, almond flour, egg, diced onion, garlic powder, parsley, paprika, thyme, salt, pepper, and Worcestershire sauce to a large bowl.

Gently mix with your hands or a fork until just combined.

Divide the mixture into 6 equal portions and shape each into an oval patty about ¾-inch thick.

Place a large skillet over medium-high heat for approximately 2 minutes.

Add the olive oil once the skillet is hot but not smoking.

Place the patties in the skillet without overcrowding them.

Cook for approximately 3–4 minutes per side, or until they develop a deep golden-brown crust.

Reduce the heat to medium and add butter to the same skillet.

Add the sliced onion and cook for approximately 6–8 minutes, stirring frequently.

Sprinkle the almond flour over the onions and stir continuously for approximately 30–60 seconds.

Slowly pour in the beef broth while whisking or stirring to loosen the browned bits from the bottom of the skillet.

Stir in Worcestershire sauce, Dijon mustard, garlic powder, thyme, and black pepper.

Place the browned Salisbury steaks back into the skillet.

Reduce the heat to medium-low, cover, and simmer for approximately 10–12 minutes.

Use an instant-read thermometer to check the thickest part of the patties.

If you want a thicker gravy, mix 1 teaspoon cornstarch with 1 tablespoon cold water and stir it into the simmering sauce.

Turn off the heat and allow the steaks to rest in the gravy for approximately 3 minutes.