Heat oven to 375° F. Heat the oil in a large saucepan over medium heat. Add the onions, ½ teaspoon salt, and ¼ teaspoon pepper and cook, stirring occasionally, until soft and beginning to brown, 12 to 15 minutes.
Add the rice and cook, stirring, for 2 minutes. Add 3½ cups water and 1½ teaspoons salt and bring to a boil. Reduce heat to low and cook, covered, until the rice is tender, 18 to 20 minutes. Let sit off the heat for 5 minutes.
Meanwhile, spread the almonds on a baking sheet. Toast in oven, tossing occasionally, until golden brown, 5 to 6 minutes. Fluff the rice with a fork and fold in the almonds and dill.