Preheat oven to 375° F. Grease a 12″ cast iron skillet (or other oven safe skillet/bakeware) with butter and set aside.
To a large bowl, add strawberries, sugar, corn starch, vanilla and lemon juice. Stir until the fruit is well coated and glossy. Pour into the skillet.
Wipe out the bowl and add in oats, flour, brown sugar, cinnamon and salt. Use clean hands to cut the butter into the dry ingredients until it clumps together and is dark in color. Scatter the oat mixture evenly on top the fruit. Place in the oven for 30 minutes or until the fruit is bubbly and the top is browned.
Best served warm with vanilla ice cream. Cover and store at room temperature for up to a day, or in the refrigerator for up to 2 days.