Preheat your oven to 375°F and grab an 8x8-inch baking dish. Toss the chopped rhubarb with both sugars and lemon zest in a bowl until the rhubarb's coated evenly. Spread it in the baking dish — it'll look like a lot, but that's exactly right. This creates the perfect base for your spring rhubarb crisp recipe.

In another bowl, combine the flour, rolled oats, cinnamon, nutmeg, and sea salt with a fork. Mix it well so the spices distribute evenly throughout the dry ingredients. This is where the crisp gets its flavor, so don't rush this step.

Pour the melted butter over the dry mixture and stir until everything's moistened and crumbly. You want it to look like wet sand, not a paste. The texture here matters because it'll become that golden, crunchy topping.

Fold in the chopped walnuts and toasted almond slivers until they're scattered throughout. Don't crush them up — you want those pieces visible so they stay crispy. Press the mixture evenly over the rhubarb layer, making sure it covers completely.

Bake for 40 minutes until the topping turns golden brown and the rhubarb starts bubbling around the edges. Don't panic if you see liquid — that's the rhubarb juices creating the perfect sauce. When I made this last week, it looked kinda soupy halfway through but thickened beautifully.

Pull it from the oven and let it cool for 15 minutes on the counter. This cooling time is crucial because it helps the filling set so it's not runny when you scoop it. I know waiting's hard, but those 15 minutes make all the difference.

Scoop into bowls and enjoy warm or at room temperature. The spring rhubarb crisp recipe tastes equally good either way, though I personally prefer it still slightly warm. Store any leftovers covered in the fridge for up to four days.