Easy Rhubarb Cake

Grease a 9" x 13" baking pan and preheat the oven to 350°F.
In the bowl of an electric mixer fitted with the paddle attachment, or by hand with a large whisk and mixing bowl, beat together the oil and sugar until emulsified. Add the eggs, vanilla, and the lemon zest. Beat until very smooth and lightened in color, about 2 minutes. (If using an electric mixer, use a medium- to medium-high setting.)
Scrape the bowl. Add the salt, baking powder, and flour and stir on low until the flour mixture is mostly combined. Add the milk and continue to mix the batter on low until smooth. Do not overmix. Stir in half the diced rhubarb.
PRO TIP: Mixing the batter on low once the flour is added serves two purposes: First, it prevents a flour "explosion" in the mixer. Second, gentle mixing prevents too much gluten from forming, keeping the cake nice and tender.
Pour the rhubarb cake batter into the prepared baking dish and use a spatula to smooth the batter evenly. Scatter the reserved chopped rhubarb all over, and then sprinkle the top of the cake with sugar (about 1 to 2 tablespoons).
Bake the cake for about 1 hour 15 minutes, or until a cake tester inserted into the center comes out clean. Cool fully.
Serve the rhubarb cake plain or with whipped cream or ice cream. Strawberry ice cream or vanilla ice cream would be particularly delicious.