Preheat the oven to 350 degrees F. Line a 9 x 13-inch baking dish with parchment paper and set aside.
In a medium-sized pot, add the raspberries, sweetened condensed milk, and cornstarch. Turn the heat to medium and bring the mixture to a simmer. Stir VERY gently for 2-3 minutes barely smashing the raspberries (so they are still mostly in tact). Remove from the heat and set aside.
In a large bowl, add the butter and white sugar. Beat on medium speed until light and creamy scraping down the sides as needed. Once the mixture is light and fluffy, add in the vanilla extract, lemon zest, lemon extract, and salt. Beat to combine. Add in the flour and beat until JUST combined. Do not over-mix.
Press a little over half of the dough into the prepared 9 x 13 pan. Pour the raspberry mixture over the top and smooth it into one even layer. Drop small pieces of the remaining dough over the raspberry mixture. (The "dough" is very thick and sticky -- don't add more flour).
Bake for 28-32 minutes, until the top is golden, remove from the oven, and then cool the bars to room temperature.
Cut into squares and enjoy. Best enjoyed within 1-2 days.