/* https://grabient.com/_emRgF2gAAhp_gGMgAAgBngG7gBngPegCXgAA?style=linearGradient&steps=6&angle=315 */

background: linear-gradient(315deg, #ff9a00 0.000%, #ff6600 20.000%, #e83000 40.000%, #ae0800 60.000%, #590000 80.000%, #000b00 100.000%);

<svg xmlns="http://www.w3.org/2000/svg" width="800" height="400" viewBox="0 0 800 400" preserveAspectRatio="none">
            <!-- https://grabient.com/_emRgF2gAAhp_gGMgAAgBngG7gBngPegCXgAA?style=linearGradient&steps=6&angle=315 -->
            <defs>
              <linearGradient id="gradient" x1="0.854" y1="0.854" x2="0.146" y2="0.146">
        <stop offset="0.000" stop-color="#ff9a00" /><stop offset="0.200" stop-color="#ff6600" /><stop offset="0.400" stop-color="#e83000" /><stop offset="0.600" stop-color="#ae0800" /><stop offset="0.800" stop-color="#590000" /><stop offset="1.000" stop-color="#000b00" />
              </linearGradient>
            </defs>
            <rect x="0" y="0" width="800" height="400" fill="url(#gradient)" />
          </svg>

["#ff9a00", "#ff6600", "#e83000", "#ae0800", "#590000", "#000b00"]

// https://grabient.com/_emRgF2gAAhp_gGMgAAgBngG7gBngPegCXgAA?style=linearGradient&steps=6&angle=315
// cosine gradient palette — https://iquilezles.org/articles/palettes/
const float STEPS = 6.0;
const float ANGLE = 315.0;

vec3 palette(float t) {
    vec3 a = vec3(-5.743, 0.374, 0.000);
    vec3 b = vec3(6.783, 0.396, 0.000);
    vec3 c = vec3(0.103, 0.443, 0.103);
    vec3 d = vec3(0.990, 0.151, 0.000);
    return a + b * cos(6.283185 * (c * t + d));
}

// N stops sampled from the palette, blended like the CSS gradient
vec3 stops(float t) {
    float n = STEPS - 1.0;
    float x = clamp(t, 0.0, 1.0) * n;
    return mix(palette(floor(x) / n), palette(min(floor(x) + 1.0, n) / n), fract(x));
}

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    vec2 p = fragCoord - 0.5 * iResolution.xy;
    // CSS angle: 0 = up, clockwise; span = CSS gradient-line length
    vec2 dir = vec2(sin(radians(ANGLE)), cos(radians(ANGLE)));
    float len = abs(iResolution.x * dir.x) + abs(iResolution.y * dir.y);
    float t = dot(p, dir) / len + 0.5;
    fragColor = vec4(stops(t), 1.0);
}

[
  [-5.743, 0.374, 0.000],
  [6.783, 0.396, 0.000],
  [0.103, 0.443, 0.103],
  [0.990, 0.151, 0.000]
]

Gradient palette editor — #ff9a00 to #000b00