In the container of a blender, pulse egg yolks, lemon juice, mustard, and salt until combined. With blender running, gradually add 1 tablespoon canola oil, one drop at a time, until mixture begins to thicken.
Gradually add remaining canola oil in a steady stream until thickened, stopping occasionally to scrape sides of container. (Add ¼ cup water as needed to thin mayonnaise.) Spoon into a medium bowl. Cover and refrigerate up to 1 week. Serve with tomatoes and white bread, if desired.
Recipe by Southern Cast Iron at https://www.southerncastiron.com/sandwich-bread-homemade-mayonnaise/