Add potatoes and 3/4 teaspoon salt to medium saucepan; cover with cold water by 1 inch. Bring to boil, reduce heat; simmer 8 minutes or until just tender but not falling apart.
Transfer potatoes to baking sheet lined with paper towels. Cool about 20 minutes or until room temperature.
Meanwhile, whisk together sour cream, lemon juice, remaining 1/4 teaspoon salt, and pepper; let chill. Arrange potatoes in even layer on large serving platter. Spoon 1/2 rounded teaspoon sour cream mixture onto each potato half; top with 1/4 teaspoon caviar.
