1/2 cup coarsely chopped hazelnuts, or walnuts, toasted (see Tip)
Preheat oven to 350 °F. Coat a 9-by-5-inch loaf pan with cooking spray; set aside.
Combine 1/2 cup apricots and nectar (or juice) in a small saucepan. Bring to a simmer, remove from heat and let stand for 10 minutes. Transfer the apricots and their liquid to a food processor and process until a chunky puree forms. (You should have about 1/2 cup puree.)
Whisk flour, baking powder, baking soda and salt in a large bowl. Whisk egg, egg whites, sugar, yogurt, oil, lemon zest, vanilla and the apricot puree in another large bowl. Stir the apricot mixture into the dry ingredients just until combined. Fold in raisins, hazelnuts and the remaining 1 cup chopped apricots. (The batter will be thick.) Turn the batter out into the prepared pan, smoothing the top.
Bake until the top is golden brown and a skewer inserted in the center comes out clean, 50 to 60 minutes. Let cool in the pan for 10 minutes. Loosen the edges and invert the loaf onto a wire rack to cool.
Tip: To toast chopped nuts: Place in a small dry skillet and cook over medium-low heat, stirring constantly, until fragrant and lightly browned, 2 to 4 minutes.