Combine pecans, sugar, corn syrup, and salt in a glass 4-cup measuring cup.
Heat in microwave for 3 1/2 minutes; stir and heat for 3 1/2 more minutes. Stir butter into pecan mixture and heat in microwave for 2 more minutes.
Stir baking soda and vanilla extract into pecan mixture until foamy; pour onto the prepared baking sheet. Allow to cool completely before breaking brittle into pieces. Store in an airtight container.