Stir the graham cracker crumbs, butter, sugar and salt together in a large bowl. Butter a 9-inch springform pan or six 3-inch tart pans. Press the crumb mixture onto the bottom and about halfway up the sides of the pan.
For the filling: Combine the sugar, salt, eggs and orange zest and juice in a large bowl and whisk to a homogeneous consistency. Transfer to a medium saucepan over medium heat. Cook, whisking constantly, until the mixture has thickened, 12 to 15 minutes. Remove from the heat and whisk in the butter, 2 pats at a time, until it's incorporated and has a silky consistency.
Pour the orange curd into the prepared tart shell and bake until the orange curd has set, about 15 minutes. Let cool completely before cutting.