Preheat oven to 350 degrees. Line baking sheet with parchment paper.
In a large mixing bowl, add in the butter and sugar. Beat on medium/high until light and fluffy.
Add in the vanilla extract and eggs one at a time. Scrape down the sides of the bowl and beat to incorporate any remaining egg.
Add in the flour and salt. Beat in the flour until it comes together into a dough. It will become dry and crumbly before it comes together.
Once it comes together into a ball, place onto a large piece of wax paper. Roll it out into a long narrow dough. I would say mine was about 20 to 24 inches long and 8 inches wide. I trimmed off the edges to make the lines straight. You can use the extra dough to fill in any gaps.
Cut the dough lengthwise so you have two 20 - 24 inch pieces of dough.
If you're using date spread, add it into a sandwich bag and pipe it into a straight line towards the edge of the dough. Do it on both of the strips of dough.
If you're using the 12 oz. container of pitted dates, add them into a food processor or blender. Blend until a ball forms. Divide the ball in half and roll each half into a 20 - 24 inch strip. Make it as long as your dough.
Roll the date spread/puree into the dough. I grab the edge of the wax paper and pull it straight up to roll the dough over the date spread/puree. Roll to the end of the dough and repeat with the second strip. I rock it back and forth a few times to even out the strip.
Pinch the strip of cookie dough as you cut slices. That will help it keep its shape rather than going flat. I sliced the cookies about an inch thick.
Place on the prepared baking sheet.
Place into the oven and bake for 12 minutes. Remove from the oven and cool for about 5 minutes before moving them to the wire rack to cool.