Curried Caramelized Onions
Slice the 2 medium onions as thinly as possible; this makes them caramelize much faster. Add them to a heavy bottomed pan with the 2 tablespoons olive oil. Add the 1 teaspoon evaporated cane sugar, 1 teaspoon garam masala and ⅛ teaspoon salt and fry over medium low heat until the onions are a deep brown color (about 40 minutes). If it starts to burn or brown unevenly, turn the heat down. When the onions are done, they should look and taste like a fragrant oniony jam. Remove from heat and stir in the 1 teaspoon lemon juice.
Merguez Lamb Burger
Put the 1 teaspoon cumin and ¼ teaspoon ground coriander seed in a pan over medium high heat and roast, shaking the pan regularly, until dark and fragrant. Use a spice grinder or a mortar and pestle to grind the spices. Combine the roasted spices with the 2 teaspoons sumac, 2 teaspoons paprika, ½ teaspoon cayenne pepper, ¼ teaspoon fennel pollen, 1 tablespoon harissa and 3 cloves garlic in a bowl and mash together into a paste.
Add the 1 lb ground lamb and use a fork to mix the paste into the lamb. If your ground lamb is very lean, add a tablespoon of olive oil to keep the meat moist. The spice mixture should be evenly distributed, but avoid over-mixing, or the finished burger will end up dense and chewy. If your harissa is as salty as mine, you won't need to add salt, but if it's not, add some salt to taste (put a small piece of lamb mixture in the microwave for a few seconds to cook it before tasting). Shape the lamb into two to four ½" thick patties.
If you made your patties ahead of time and refrigerated, take them out of the fridge about 20 minutes before you are ready to cook them so they come to room temperature; this ensures they will cook evenly. If you are grilling the lamb burgers, get the grill nice and hot and grill each side until golden brown. The burgers are best when cooked to about medium, otherwise they will start to get dry. If you are using a broiler, move the rack to the top position and put a wire rack on a cookie sheet and preheat under the boiler. When the rack is nice and hot, place the patties on it and broil each side until golden brown.
To assemble your burger, toast 2 - 4 buns, put down a thin layer of harissa on one side of the bun, put your Merguez lamb burger on the bun and top with caramelized onions. If your harissa is too pasty to spread evenly, just mix it with some olive oil or mayonnaise.