Peel the potatoes and shred them in a food processor fitted with the shredding blade; transfer the potatoes to a large bowl as the food processor fills up. Repeat with the onion. Transfer the onion to the bowl with the potatoes and stir in the matzo meal, egg, baking powder and salt.
Fill a large skillet with 1/2 inch oil. Heat over medium-high heat until the oil is very hot but not smoking. To test if the oil is hot enough, drop a small piece of potato into the oil; if the potato sizzles steadily, the oil is ready.
Working in batches, scoop the potato mixture by 1/4-cupfuls and add them carefully to the skillet, flattening each latke slightly with a spatula. Fry, turning the latkes once, until golden brown and cooked through, about 3 minutes. Drain on paper towels. Remove any loose bits of potato mixture between batches with a slotted spoon.
Serve the latkes immediately, or keep them warm in a 200 degree F oven. Garnish with fresh herbs and serve with sour cream and Spiced Apple-Pear Sauce.
Spiced Apple-Pear Sauce:
Combine the apples, pears, lemon juice, cinnamon sticks, nutmeg, 1 tablespoon sugar and 1/4 cup water in a medium saucepan. Bring to a boil over medium-high heat. Cover, reduce the heat to medium-low and cook until the apples and pears are very soft but still a bit chunky, 15 to 20 minutes. Taste the mixture and add the remaining tablespoon of sugar if desired.
Remove the sauce from the heat and stir a few times until the sauce is well combined with small chunks. Cool to room temperature. Remove the cinnamon sticks and serve. (For a smoother sauce, remove from heat, remove the cinnamon sticks and then whisk the mixture until smooth before cooling.)
If you need to fry a lot of latkes, it's best to make multiple batches rather than one double batch. The longer the mixture sits, the wetter it becomes which makes the latkes fall apart more easily as they cook.