Preheat the oven to 350 degrees F (175 degrees C).
Fit 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 stiff. Gradually add remaining 1/4 cup sugar and cream of tartar, continuing to beat until meringue is glossy.
Remove pie from the oven; spoon meringue over top, covering the entire filling. Use a spoon or spatula to make decorative swirls in meringue.
Return to the oven and bake until meringue is lightly browned, about 10 minutes. Cool for 10 to 15 minutes before serving.