When Tyler Florence was creating hamburgers for his new restaurant, his goal was simple — a burger that stays moist no matter how well-done it is cooked.

The solution was all a matter of numbers — one month of experimenting with the percentage of fat and the number of cuts of meat.

"Most people do an 80-20 lean-to-fat ratio," Florence, whose Wayfare Tavern opened recently in San Francisco, said in a telephone interview. "We go 75-to-25 ratio, so it's a little fattier. So even if you like it well done, it's still nice and moist."

For the cuts of meat, Florence settled on four of them — prime rib, brisket, skirt steak and filet. And after they are ground (at another facility), it's mostly a hands-off procedure.

"When it comes in, no one is really allowed to touch it except to take it out of the package and weigh it out," said Florence, host of Food Network's "The Great Food Truck Race." "It gets touched once before it goes on the grill. It loses that fluffiness once you work it too much. It starts to become chewy really quickly."

Florence was equally exacting when it came toppings.

"You can't just put stuff on top of the burger for the sake of it," he said. "To me, it's got to be very purposeful stuff. You have to really think it through so it's a complimentary flavour and not a distraction from the burger."

For the AP's 20 Burgers of Summer series, Florence opted for an intensely savoury and creamy combination of oven-roasted red onions, lemon aioli and brie.

Wayfare Tavern Burger Buns

Start to finish: 2 1/2 hours (20 minutes active)

250 ml (1 cup) warm water

50 ml (1/4 cup) warm whole milk

1 pkg (7 g/1/4 oz) active dry yeast

37 ml (2 1/2 tbsp) sugar

2 eggs

750 ml (3 cups) bread flour

75 ml (1/3 cup) all-purpose flour

7 ml (1 1/2 tsp) salt

37 ml (2 1/2 tbsp) unsalted cold butter, cut into 5-mm (1/4-inch) pieces

In a medium bowl, combine water, milk, yeast and sugar until well blended. Let stand until foamy, about 5 minutes.

In a small bowl, lightly beat one of the eggs.

In a large bowl, whisk together bread flour, all-purpose flour and salt.

Gradually add butter, beaten egg and yeast mixture, mixing with a pastry scraper or clean hands until a sticky dough forms.

Knead this mixture on a clean, well-floured surface for 6 to 8 minutes or until dough is smooth.

Place dough in a large bowl, cover with a clean towel and let stand for 1 to 1 1/2 hours or until dough has doubled in size.

Divide dough into 8 portions. Roll each portion into a ball and place on a parchment-lined baking sheet about 5 cm (2 inches) apart. Cover pan loosely with plastic wrap and let stand for another hour or until the rolls have risen slightly.

When ready to bake, place a large shallow pan of water on the floor of the oven and heat oven to 200 C (400 F).

In a small bowl, lightly beat remaining egg with 15 ml (1 tbsp) water. Brush mixture over top of each roll. Bake rolls for 15 to 20 minutes or until golden.

Transfer rolls to a rack and let cool completely.

Makes 8 buns.

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Wayfare Tavern Lemon Aioli

Start to finish: 5 minutes

1 egg yolk

Juice of 1/2 lemon

150 ml (2/3 cup) grapeseed oil

Salt and ground black pepper

In a food processor, combine yolk and lemon juice. Pulse until just combined.

With processor running, gradually pour in grapeseed oil. Process until mixture is creamy and emulsified.

Season with salt and pepper, then cover and chill until ready to serve.

Makes 250 ml (1 cup).

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Wayfare Tavern Burger

Start to finish: 20 minutes

250 g (1/2 lb) ground prime rib

500 g (1 lb) ground brisket

500 g (1 lb) ground skirt steak

250 g (1/2 lb) ground filet

8 hamburger buns (recipe above)

Kosher salt and pepper

1 large red onion, sliced into 5-mm (1/4-inch) rings

250 ml (1 cup) lemon aioli (recipe above)

250 g (1/2 lb) brie, cut into thin slices

In a large bowl, mix prime rib, brisket, skirt steak and filet together until well blended, but not overworked.

Divide meat into 8 portions and shape into patties. Season with salt and pepper.

Heat oven to 200 C (400 F). Line a baking sheet with parchment paper.

Arrange onion slices in a single layer on prepared pan. Roast onion slices for 10 to 12 minutes or until tender. Set aside.

Heat grill on high.

Grill burgers to desired doneness, about 4 minutes on each side for medium-rare.

Top bottom half of each roll with a burger, some of the red onions, aioli and brie.

Makes 8 servings.

Nutrition information per serving (values are rounded to the nearest whole number): 1,078 calories; 560 calories from fat; 63 g fat (22 g saturated; 0 g trans fats); 232 mg cholesterol; 68 g carbohydrate; 58 g protein; 3 g fibre; 921 mg sodium.