Preheat the oven to 350 degrees F (175 degrees C).

Press pie crust into a 9-inch pie dish; spread rhubarb evenly over crust.

Whisk 1 cup sugar, half-and-half, egg yolks, flour, and salt together in a bowl until smooth; pour over rhubarb.

Bake in the preheated oven until crust is browned and filling is set, 50 to 60 minutes.

Just before pie is finished baking, beat egg whites in a glass, metal, or ceramic bowl until foamy. Gradually add remaining 1/4 cup sugar and cream of tartar, continuing to beat until meringue is glossy and stiff peaks form.

Remove pie from the oven; spoon meringue over top, covering the entire filling. Make decorative swirls in meringue using a spoon or spatula.

Return to the oven; bake until meringue is lightly browned, about 10 minutes. Cool for 10 to 15 minutes before serving.