Rectangle

<svg
    xmlns="http://www.w3.org/2000/svg"
    width="512"
    height="512"
    viewBox="0 0 512 512"
>
    <radialGradient
        id="a"
        cx="431.157"
        cy="1294.331"
        r="211.111"
        gradientTransform="matrix(.931 0 0 .114 -148.108 233.509)"
        gradientUnits="userSpaceOnUse"
    >
        <stop offset="0" stop-color="#fff8be" />
        <stop offset=".512" stop-color="#fffbe5" />
        <stop offset=".976" stop-color="#fff" />
    </radialGradient>
    <radialGradient
        id="b"
        cx="-20.83"
        cy="117.886"
        r="256.461"
        gradientTransform="matrix(-.094 .996 -.507 -.048 36.941 144.261)"
        gradientUnits="userSpaceOnUse"
    >
        <stop offset="0" stop-color="#fff9e2" />
        <stop offset=".514" stop-color="#fffacd" />
        <stop offset=".976" stop-color="#fff6ab" />
    </radialGradient>
    <radialGradient
        id="c"
        cx="376.885"
        cy="194.453"
        r="415.649"
        gradientTransform="matrix(1 0 0 .726 0 53.343)"
        gradientUnits="userSpaceOnUse"
    >
        <stop offset="0" stop-color="#fff044" />
        <stop offset=".449" stop-color="#ffea00" />
        <stop offset=".647" stop-color="#fbd113" />
        <stop offset=".976" stop-color="#f6ab31" />
    </radialGradient>
    <path
        fill="url(#a)"
        d="M256 406.4c113.107 0 204.798-11.462 204.798-25.6H51.202c0 14.138 91.691 25.6 204.798 25.6z"
    />
    <path fill="url(#b)" d="M0 105.6v275.2h38.4l38.4-243.2-38.4-32z" />
    <path fill="url(#c)" d="M38.4 105.6H512v275.2H38.4z" />
</svg>