Orange Lemon Frosting

This is Cleone's recipe:

2 tsp Orange Rind
1/2 tsp Grated Lemon Rind
3 tbsp Butter
1 egg, unbeaten
Dash of salt
3 1/2 cups Powdered Sugar
2 tbsp Orange Juice
1 tbsp Lemon Juice

Add orange and lemon rinds to butter and cream well. Add egg and salt and blend. Add sugar alternately with fruit juice, beating until right consistency.