Raspberry Rhubarb Streusel Pie Bars are the perfect introduction to Spring baking. I love the sweet-tart, jammy filling with the buttery press-in crust, and oat streusel topping that adds a nice crunch. This post is sponsored by Lodge Cast Iron, and I’ve used their Casserole Pan to make the pie bars, which ensures a crisp crust and even baking, and the handles make it easy to get the pan in and out…