Tarama is salted and cured carp or cod roe used in Greek and Turkish cooking. It ranges in color from orange-red to pale beige and can be found online or at specialty or Mediterranean markets.
Place roe in a bowl, and cover with cold water. Soak for 10 minutes. Drain in a fine sieve lined with cheesecloth. Rinse in sieve, and drain. Gather cheesecloth around roe, and squeeze out water.
Meanwhile, place potato in a small saucepan, and add enough cold water to cover by 2 inches. Add salt. Bring to a boil, and cook until tender, about 5 minutes. Drain, and let cool.
Puree roe, potato, lemon juice, and pepper in a food processor. With machine running, add oil, and process until the mixture is smooth. Season with more pepper. Serve with toasts and crudites.