Meringue is a cook’s miracle. Mostly egg whites and air, this cloudlike mass is easy to create. But a speck of fat can ruin the whole thing. Make sure there’s no yolk in there, and wipe your tools with vinegar to remove any traces of oil or fat.
Preheat oven to 350°. Spread almonds on a cookie sheet and toast 5 minutes. Cool, then chop roughly. Toss ½ cup almonds with confectioners’ sugar, reserving remaining ¼ cup for garnish; set nuts aside.
Reduce oven to 225°. Wet a paper towel with white vinegar and wipe the bowl and whisk of a mixer. Place egg whites in bowl, add cream of tartar and salt, then whisk on medium-high speed until foamy, about 1 minute. Gradually add granulated sugar in a very slow stream while whisking, until meringue is glossy and forms stiff peaks, about 2 minutes. Gently fold in the sugared almonds with a spatula. Drop tablespoons of batter onto a cookie sheet lined with parchment paper or nonstick baking pad. Bake 1-½ hours. Turn oven off. Let meringues stand in closed oven with the light on at least 4 hours or overnight. Garnish with the remaining almonds. Store in an airtight container.