woocommerce/plugins/woocommerce-blocks/assets/js/base/components/cart-checkout/button/style.scss

// Extra classes are added for specificity.
.wc-block-cart,
.wc-block-checkout {
	.button.wc-block-button {
		align-items: center;
		background-color: $black;
		color: $white;
		display: flex;
		font-size: inherit;
		font-weight: bold;
		height: 48px; // same height as text-input
		justify-content: center;
		line-height: 1;
		padding: 0 $gap-small;
		text-align: center;
		text-decoration: none;
		text-transform: none;

		&:hover,
		&:focus,
		&:active {
			background-color: $black;
			color: $white;
		}
	}
}