How to Make It
Halve the zucchini crosswise. Cut the zucchini flesh off the seedy center and coarsely grate it in a food processor. Or grate it on a box grater until you reach the seedy center. Discard the center. In a food processor or on a box grater, coarsely grate the potato and onion. Transfer the grated zucchini, potato and onion to a colander and squeeze dry. Let stand for 2 minutes, then squeeze again. Transfer the vegetable mixture to a large bowl. Add the matzo meal, egg, lemon juice, salt and pepper and stir to combine.
In a medium skillet, heat 2 tablespoons of vegetable oil until shimmering. Drop packed teaspoons of the zucchini mixture into the skillet and flatten them with the back of a spoon. Cook the latkes over moderately high heat until the edges are golden, about 1 1/2 minutes; flip and cook until golden on the bottom, about 1 minute. Drain on paper towels. Repeat with the remaining zucchini mixture, adding more oil to the skillet as needed.
Arrange the latkes on a platter and top each one with a dollop of sour cream and a little red pepper jelly, smoked trout and golden trout roe; sprinkle with the scallion greens. Serve warm.
Golden trout roe is available at specialty food stores.