Clean the butcher block thoroughly to remove any dirt or debris.
Lightly sand any rough edges that may surround the split.
Fill the split with a wood filler compound. Wood fillers can be found at hardware and home improvement stores and come in various shades.
Smooth the filler and make sure there are no air bubbles. Let the compound dry overnight.
Lightly sand the area and apply a butcher block oil to the countertop.