Briefly heat the apricot preserves in a heavy-bottomed pan under medium heat or in a microwave on high, until boiling. Then, rub mixture through a sieve to remove any lumps or seeds. With a pastry brush, brush on cake while still hot. If it gets too cold and solid, briefly reheat again. Brush carefully over the cake or tart with a pastry brush. Let set. Glaze will dry to a hard finish in 15 minutes or less.