Preheat the oven to 350°/180°C, and lightly grease a 8x8 inch pan or a 7.5x10.5 inch pan.
In a large bowl, combine the pear slices with lemon juice and vanilla extract. Then add cinnamon, sugar, salt and flour and toss everything together until well combined.
To make the topping, in a bowl combine the flour with brown sugar and cinnamon. Then add the cubed cold butter, and mix it in using a pastry cutter, a fork or your hands (just like pie crust), you want to cut in the butter until the mixture resembles wet sand.
Add the oats, and mix them in with the mixture.
Transfer the pears to the prepared baking dish (use a spatula to gently even it out), then evenly spread the topping over the pears. Bake for 40-45 minutes or until the topping is golden brown.
Serve warm with a scoop of ice cream and enjoy.