Line a 9" x 13" pan with enough parchment paper to go about 1" up on all sides. In the work bowl of a food processor, add the flour, rolled oats, powdered sugar, salt and vanilla seeds. Pulse a few times to combine, then add the butter and pulse until the dough looks like pea sized gravel (about ten, one second bursts). Sprinkle the dough evenly over the parchment lined sheet and use your fingers to press the dough into a uniform sheet of dough that goes about 1/2" up all the sides. Put it in the freezer for 30 minutes. Meanwhile, place the oven rack in the middle position and preheat the oven to 350 degrees F.
In a small bowl, combine the strawberries and 1/4 cup of sugar and toss to coat. This will release excess moisture and sweeten the strawberries. To prepare the filling, whisk together the eggs, sugar, flour and lemon zest. Add the lemon juice and whisk to combine.
Remove the crust from the freezer and put in oven and bake for around 25 minutes, or until it is golden brown and fragrant. When the crust is done, take it out of the oven, then immediately scatter the strawberries around the crust, pour any accumulated juices into the lemon mixture and whisk to combine. Pour the lemon mixture over the strawberries.
Lower the oven temperature to 325 degrees F, then put the pan in the oven and bake for about 20 minutes, or until the center of the lemon bars doesn't jiggle anymore. Remove from the oven and allow them to cool completely. Slice, then dust with powdered sugar and serve.